Variable magnification optical system, optical device, and method for producing variable magnification optical system

ABSTRACT

A variable magnification optical system has, in order from an object side: a first lens group having positive refractive power; a second lens group having negative refractive power; an aperture stop; a third lens group having positive refractive power; and a rear lens group. Upon zooming from a wide-angle end state to a telephoto end state, at least the rear lens group is moved toward the object side, and distances between the lens groups are varied. Upon focusing from an infinitely distant object to a closely distant object, the third lens group is moved along the optical axis. At least a portion of the rear lens group constitutes a vibration reduction lens group having negative refractive power and moveable perpendicular to the optical axis. An optical apparatus and a method of manufacture are also provided.

TECHNICAL FIELD

The present invention relates to a variable magnification opticalsystem, an optical device, and a producing method for the variablemagnification optical system.

BACKGROUND ART

There has been proposed a variable magnification optical system suitablefor a photographing camera, an electronic still camera, a video cameraor the like, for example, in Japanese Patent application Laid-Open No.2009-251114 and in Japanese Patent application Laid-Open No.2010-237455.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent application Laid-Open Gazette No.2009-251114

Patent Document 2: Japanese Patent application Laid-Open Gazette No.2010-237455

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the conventional variable magnification optical system asdescribed above, there was a problem that excellent correction ofaberrations could not have been realized.

The present invention is made in view of the above-described problem,and has an object to provide a variable magnification optical systemcapable of realizing excellent optical performance, an opticalapparatus, and a method for manufacturing the variable magnificationoptical system.

Means for Solving the Problem

In order to solve the above-mentioned object, according to a firstaspect of the present invention, there is provided a variablemagnification optical system comprising, in order from an object side: afirst lens group having positive refractive power; a second lens grouphaving negative refractive power; an aperture stop; a third lens grouphaving positive refractive power; and a rear lens group;

upon zooming from a wide-angle end state to a telephoto end state, atleast the rear lens group being moved toward the object side; and adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group, and adistance between the third lens group and the rear lens group beingvaried;

upon focusing on from an infinite distant object to a close distantobject, the third lens group as a whole being moved in the direction ofthe optical axis;

at least a portion of the rear lens group being moved as a vibrationreduction lens group so as to have a component in a directionperpendicular to the optical axis; and

the vibration reduction lens group having negative refractive power.

Further, according to a second aspect of the present invention, there isprovided an optical apparatus equipped with the variable magnificationoptical system according to the first aspect of the present invention.

Further, according to a third aspect of the present invention, there isprovided a variable magnification optical system comprising, in orderfrom an object side: a first lens group having positive refractivepower; a second lens group having negative refractive power; a thirdlens group having positive refractive power; and a rear lens group;

upon zooming from a wide-angle end state to a telephoto end state, atleast the first lens group and the rear lens group being moved towardthe object side; and a distance between the first lens group and thesecond lens group, a distance between the second lens group and thethird lens group, and a distance between the third lens group and therear lens group being varied;

upon focusing on from an infinite distant object to a close distantobject, the third lens group as a whole being moved in the direction ofthe optical axis;

at least a portion of the rear lens group being moved as a vibrationreduction lens group to have a component in a direction perpendicular tothe optical axis;

the vibration reduction lens group having negative refractive power; and

the following conditional expression being satisfied:0.20<(−fVR)/f3<1.20where fVR denotes a focal length of the vibration reduction lens group,and f3 denotes a focal length of the third lens group.

Further, according to a fourth aspect of the present invention, there isprovided an optical apparatus equipped with the variable magnificationoptical system according to the third aspect of the present invention.

Further, according to a fifth aspect of the present invention, there isprovided a variable magnification optical system comprising, in orderfrom an object side: a first lens group having positive refractivepower; a second lens group having negative refractive power; an aperturestop; a third lens group having positive refractive power; and a rearlens group;

the third lens group being composed of a cemented lens constructed by apositive lens cemented with a negative lens;

upon zooming from a wide-angle end state to a telephoto end state, atleast the rear lens group being moved toward the object side, and adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group, and adistance between the third lens group and the rear lens group beingvaried;

upon focusing on from an infinite distant object to a close distantobject, the third lens group as a whole being moved in the direction ofthe optical axis.

Further, according to a sixth aspect of the present invention, there isprovided an optical apparatus equipped with the variable magnificationoptical system according to the fifth aspect of the present invention.

Further, according to a seventh aspect of the present invention, thereis provided a variable magnification optical system comprising, in orderfrom an object side: a first lens group having positive refractivepower; a second lens group having negative refractive power; a thirdlens group having positive refractive power; and a fourth lens grouphaving positive refractive power;

upon zooming from a wide-angle end state to a telephoto end state, adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group, and adistance between the third lens group and the fourth lens group beingvaried; and

the variable magnification optical system having at least one lens thatsatisfies the following conditional expressions:1.928<ndh28.60<νdhwhere ndh denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe lens, and νdh denotes Abbe number at d-line (wavelength λ=587.6 nm)of the lens.

Further, according to an eighth aspect of the present invention, thereis provided an optical apparatus equipped with the variablemagnification optical system according to the seventh aspect of thepresent invention.

Further, according to a ninth aspect of the present invention, there isprovided a method for manufacturing a variable magnification opticalsystem comprising, in order from an object side: a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; an aperture stop; a third lens group having positiverefractive power; and a rear lens group;

the method comprising the steps of:

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, at least the rear lens group is moved toward anobject side, and a distance between the first lens group and the secondlens group, a distance between the second lens group and the third lensgroup, and a distance between the third lens group and the rear lensgroup are varied;

constructing such that, upon focusing on from an infinite distant objectto a close distant object, the third lens group as a whole is moved inthe direction of the optical axis;

constructing such that at least a portion of the rear lens group ismoved as a vibration reduction lens group so as to have a component in adirection perpendicular to the optical axis; and

constructing the vibration reduction lens group to have negativerefractive power.

Further, according to a tenth aspect of the present invention, there isprovided a method for manufacturing a variable magnification opticalsystem comprising, in order from an object side: a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; a third lens group having positive refractive powerand a rear lens group;

the method comprising the steps of:

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, at least the first lens group and the rear lensgroup are moved toward an object side, and a distance between the firstlens group and the rear lens group, a distance between the second lensgroup and the third lens group and a distance between the third lensgroup and the rear lens group are varied;

constructing such that, upon focusing on from an infinite distant objectto a close distant object, the third lens group as a whole is moved inthe direction of the optical axis;

constructing such that at least a portion of the rear lens group ismoved as a vibration reduction lens group to have a component in adirection perpendicular to the optical axis;

constructing the vibration reduction lens group to have negativerefractive power; and

constructing the third lens group and the vibration reduction lens groupto satisfy the following conditional expression:0.20<(−fVR)/f3<1.20where fVR denotes a focal length of the vibration reduction lens group,and f3 denotes a focal length of the third lens group.

Further, according to an eleventh aspect of the present invention, thereis provided a method for manufacturing a variable magnification opticalsystem comprising, in order from an object side: a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; an aperture stop; a third lens group having positiverefractive power; and a rear lens group having positive refractivepower;

the method comprising the steps of:

constructing such that the third lens group is composed of a cementedlens constructed by a positive lens cemented with a negative lens;

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, at least a distance between the first lens groupand the second lens group, a distance between the second lens group andthe third lens group, and a distance between the third lens group andthe rear lens group are varied; and

constructing such that, upon focusing on from an infinite distant objectto a close distant object, the third lens group as a whole is moved inthe direction of the optical axis.

Further, according to a twelfth aspect of the present invention, thereis provided a variable magnification optical system comprising, in orderfrom an object side: a first lens group having positive refractivepower; a second lens group having negative refractive power; a thirdlens group having positive refractive power; and a fourth lens grouphaving positive refractive power;

constructing the variable magnification optical system to have at leastone lens that satisfies the following conditional expressions:1.928<ndh28.60<νdhwhere ndh denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe lens, and νdh denotes Abbe number at d-line (wavelength λ=587.6 nm)of the lens; and

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group, a distance between the second lens group and thethird lens group, and a distance between the third lens group and thefourth lens group are varied.

Effect of the Invention

According to the first to the sixth aspects and the ninth to theeleventh aspects of the present invention, there are provided a variablemagnification which has high variable magnification ratio, is compactand has excellent optical performance, an optical apparatus, and amethod for manufacturing a variable magnification optical system.

According to the seventh, eighth and twelfth fourth aspects of thepresent invention, there are provided a variable magnification opticalsystem which is compact and has excellent optical performance, anoptical apparatus, and a method for manufacturing a variablemagnification optical system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are sectional views showing a variable magnificationoptical system according to a First Example that is common to a first tothird embodiments of the present application, in which FIG. 1A showssectional view in a wide-angle end state, FIG. 1B shows sectional viewin an intermediate focal length state, and FIG. 1C shows sectional viewin a telephoto end state.

FIGS. 2A, 2B and 2C are graphs showing various aberrations of thevariable magnification optical system according to the First Example ofthe present application upon focusing on an infinite distance object, inwhich FIG. 2A shows various aberrations in the wide-angle end state,FIG. 2B shows various aberrations in the intermediate focal lengthstate, and FIG. 2C shows various aberrations in the telephoto end state.

FIGS. 3A and 3B are graphs showing meridional transverse aberration ofthe variable magnification optical system according to the First Exampleof the present application upon focusing on an infinitely distant objectand conducting vibration reduction, in which FIG. 3A shows meridionaltransverse aberration in the wide-angle end state, and FIG. 3B showsmeridional transverse aberration in the telephoto end state.

FIGS. 4A, 4B and 4C are sectional views showing a variable magnificationoptical system according to a Second Example that is common to the firstto third embodiments of the present application, in which FIG. 4A showssectional view in a wide-angle end state, FIG. 4B shows sectional viewin an intermediate focal length state, and FIG. 4C shows sectional viewin a telephoto end state.

FIGS. 5A, 5B and 5C are graphs showing various aberrations of thevariable magnification optical system according to the Second Example ofthe present application upon focusing on an infinitely distant object,in which FIG. 5A shows various aberrations in the wide-angle end state,FIG. 5B shows various aberrations in the intermediate focal lengthstate, and FIG. 5C shows various aberrations in the telephoto end state.

FIGS. 6A and 6B are graphs showing meridional transverse aberration ofthe variable magnification optical system according to the SecondExample of the present application upon focusing on an infinitelydistant object and conducting vibration reduction, in which FIG. 6Ashows meridional transverse aberration in the wide-angle end state, andFIG. 6B shows meridional transverse aberration in the telephoto endstate.

FIGS. 7A, 7B and 7C are sectional views showing a variable magnificationoptical system according to a Third Example that is common to the firstto third embodiments of the present application, in which FIG. 7A showssectional view in a wide-angle end state, FIG. 7B shows sectional viewin an intermediate focal length state, and FIG. 7C shows sectional viewin a telephoto end state.

FIGS. 8A, 8B and 8C are graphs showing various aberrations of thevariable magnification optical system according to the Third Example ofthe present application upon focusing on an infinitely distant object,in which FIG. 8A shows various aberrations in the wide-angle end state,FIG. 8B shows various aberrations in the intermediate focal lengthstate, and FIG. 8C shows various aberrations in the telephoto end state.

FIGS. 9A and 9B are graphs showing meridional transverse aberration ofthe variable magnification optical system according to the Third Exampleof the present application upon focusing on an infinitely distant objectand conducting vibration reduction, in which FIG. 9A shows meridionaltransverse aberration in the wide-angle end state, and FIG. 9B showsmeridional transverse aberration in the telephoto end state.

FIGS. 10A, 10B and 10C are sectional views showing a variablemagnification optical system according to a Fourth Example of the fourthembodiment of the present application, in which FIG. 10A shows sectionalview in a wide-angle end state, FIG. 10B shows sectional view in anintermediate focal length state, and FIG. 10C shows sectional view in atelephoto end state.

FIGS. 11A, 11B and 11C are graphs showing various aberrations of thevariable magnification optical system according to the Fourth Example ofthe present application upon focusing on an infinitely distant object,in which FIG. 11A shows various aberrations in the wide-angle end state,FIG. 11B shows various aberrations in the intermediate focal lengthstate, and FIG. 11C shows various aberrations in the telephoto endstate.

FIGS. 12A, 12B and 12C are sectional views showing a variablemagnification optical system according to a Fifth Example of the fourthembodiment of the present application, in which FIG. 12A shows sectionalview in a wide-angle end state, FIG. 12B shows sectional view in anintermediate focal length state, and FIG. 12C shows sectional view in atelephoto end state.

FIGS. 13A, 13B and 13C are graphs showing various aberrations of thevariable magnification optical system according to the Fifth Example ofthe present application upon focusing on an infinitely distant object,in which FIG. 13A shows various aberrations in the wide-angle end state,FIG. 13B shows various aberrations in the intermediate focal lengthstate, and FIG. 13C shows various aberrations in the telephoto endstate.

FIGS. 14A, 14B and 14C are sectional views showing a variablemagnification optical system according to a Sixth Example the fourthembodiment of the present application, in which FIG. 14A shows sectionalview in a wide-angle end state, FIG. 14B shows sectional view in anintermediate focal length state, and FIG. 14C shows sectional view in atelephoto end state.

FIGS. 15A, 15B and 15C are graphs showing various aberrations of thevariable magnification optical system according to the Sixth Example ofthe present application upon focusing on an infinitely distant object,in which FIG. 15A shows various aberrations in the wide-angle end state,FIG. 15B shows various aberrations in the intermediate focal lengthstate, and FIG. 15C shows various aberrations in the telephoto endstate.

FIGS. 16A, 16B and 16C are sectional views showing a variablemagnification optical system according to a Seventh Example the fourthembodiment of the present application, in which FIG. 16A shows sectionalview in a wide-angle end state, FIG. 16B shows sectional view in anintermediate focal length state, and FIG. 16C shows sectional view in atelephoto end state.

FIGS. 17A, 17B and 17C are graphs showing various aberrations of thevariable magnification optical system according to the Seventh Exampleof the present application upon focusing on an infinitely distantobject, in which FIG. 17A shows various aberrations in the wide-angleend state, FIG. 17B shows various aberrations in the intermediate focallength state, and FIG. 17C shows various aberrations in the telephotoend state.

FIGS. 18A, 18B and 18C are sectional views showing a variablemagnification optical system according to a Eighth Example the fourthembodiment of the present application, in which FIG. 18A shows sectionalview in a wide-angle end state, FIG. 18B shows sectional view in anintermediate focal length state, and FIG. 18C shows sectional view in atelephoto end state.

FIGS. 19A, 19B and 19C are graphs showing various aberrations of thevariable magnification optical system according to the Eighth Example ofthe present application upon focusing on an infinitely distant object,in which FIG. 19A shows various aberrations in the wide-angle end state,FIG. 19B shows various aberrations in the intermediate focal lengthstate, and FIG. 19C shows various aberrations in the telephoto endstate.

FIG. 20 is a view showing a configuration of a camera equipped with thevariable magnification optical system according to the first to fourthembodiments.

FIG. 21 is a flowchart schematically explaining a method formanufacturing the variable magnification optical system according to thefirst embodiment of the present application.

FIG. 22 is a flowchart schematically explaining a method formanufacturing the variable magnification optical system according to thesecond embodiment of the present application.

FIG. 23 is a flowchart schematically explaining a method formanufacturing the variable magnification optical system according to thethird embodiment of the present application.

FIG. 24 is a flowchart schematically explaining a method formanufacturing the variable magnification optical system according to thefourth embodiment of the present application.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

The variable magnification optical system, the optical apparatus and themethod for manufacturing the variable magnification optical systemaccording to the first embodiment of the present application isexplained below.

The variable magnification optical system according to the firstembodiment of the present application comprises, in order from an objectside: a first lens group having positive refractive power; a second lensgroup having negative refractive power; an aperture stop; a third lensgroup having positive refractive power; and a rear lens group;

upon zooming from a wide-angle end state to a telephoto end state, atleast the rear lens group being moved toward the object side; and adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group, and adistance between the third lens group and the rear lens group beingvaried;

upon focusing on from an infinite distant object to a close distantobject, the third lens group as a whole being moved in the direction ofthe optical axis;

at least a portion of the rear lens group being moved as a vibrationreduction lens group so as to have a component in a directionperpendicular to the optical axis; and

the vibration reduction lens group having negative refractive power.

In the variable magnification optical system according to the firstembodiment of the present application, the third lens group is disposedin the neighborhood of the aperture stop, and focusing on from aninfinite distant object to a close distant object, is carried out bymoving the third lens group as a whole in the direction of the opticalaxis. Due to such configuration, variation in curvature of field can besuppressed upon focusing a closely distant object, so it is preferable.

In the variable magnification optical system according to the firstembodiment of the present application, at least a portion of the rearlens groups is moved, as a vibration reduction lens group, to have acomponent in a direction perpendicular to the optical axis, and thevibration reduction lens group has negative refractive power. Due tothis configuration, correction of image blur upon camera shake beingcaused, that is, vibration reduction, can be conducted. Further,vibration reduction can be conducted by a small-sized lens group, so amechanism for the vibration reduction can be made downsized and small inweight, thereby a lens barrel being able to be downsized. It ispreferable.

Due to the above mentioned configuration, a variable magnificationoptical system having high zoom ratio, being downsized, and havingexcellent optical performance can be realized.

In the variable magnification optical system according to the firstembodiment of the present application, it is preferable that thefollowing conditional expression (1) is satisfied:0.60<f1/f3<2.60  (1)where f1 denotes a focal length of the first lens group, and f3 denotesa focal length of the third lens group.

The conditional expression (1) defines the focal length of the firstlens group relative to the focal length of the third lens group. Withsatisfying the conditional expression (1), the variable magnificationoptical system according to the first embodiment of the presentapplication is capable of correcting superbly spherical aberration uponfocusing on a closely distant object in the telephoto end state andspherical aberration in the telephoto end state.

When the value of f1/f3 of the conditional expression (1) of thevariable magnification optical system according to the first embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (1) to 2.50.

On the other hand, when the value of f1/f3 of the conditional expression(1) of the variable magnification optical system according to the firstembodiment of the present application is equal to or falls below thelower limit, refractive power of the first lens group increases. Thus,spherical aberration is generated in the telephoto end state, so that itis not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the lower limit valueof the conditional expression (1) to 0.40.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is preferable that thefollowing conditional expression (2) is satisfied:5.00<f1/(−f2)<10.00  (2)where f1 denotes the focal length of the first lens group, and f2denotes a focal length of the second lens group.

The conditional expression (2) defines the focal length of the firstlens group relative to the focal length of the second lens group. Withsatisfying the conditional expression (2), the variable magnificationoptical system according to the first embodiment of the presentinvention is capable of correcting superbly spherical aberration uponfocusing in the wide-angle end state and spherical aberration in thetelephoto end state.

When the value of f1/(−f2) of the conditional expression (2) of thevariable magnification optical system according to the first embodimentof the present application is equal to or exceeds the upper limit,refractive power of the second lens group becomes large, and it becomesdifficult to correct curvature of field in the wide-angle end state. Itis not preferable. Meanwhile, in order to attain the advantageous effectof the present application more surely, it is preferable to set theupper limit value of the conditional expression (2) to 8.00.

On the other hand, when the value of f1/(−f2) of the conditionalexpression (2) of the variable magnification optical system according tothe first embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the first lens group becomeslarge. Thus, spherical aberration is generated in the telephoto endstate, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (2) to 6.00.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is preferable that thefollowing conditional expression (3) is satisfied:0.20<(−fVR)/f3<1.20  (3)where fVR denotes a focal length of the vibration reduction lens group,and f3 denotes the focal length of the third lens group.

The conditional expression (3) defines the focal length of the vibrationreduction lens group relative to the focal length of the third lensgroup. With satisfying the conditional expression (3), the variablemagnification optical system according to the first embodiment of thepresent invention is capable of correcting superbly spherical aberrationupon focusing on a closely distant object in the telephoto end state andeccentric coma aberration upon conducting the vibration reduction.

When the value of (−fVR)/f3 of the conditional expression (3) of thevariable magnification optical system according to the first embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (3) to 1.00.

On the other hand, when the value of (−fVR)/f3 of the conditionalexpression (3) of the variable magnification optical system according tothe first embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the vibration reduction lensgroup increases. Thus, eccentric coma aberration is generated uponconducting the vibration reduction, so that it is not desirable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the lower limit valueof the conditional expression (3) to 0.40.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is preferable that thefollowing conditional expression (4) is satisfied:0.10<(−f2)/f3<0.38  (4)where f2 denotes the focal length of the second lens group, and f3denotes the focal length of the third lens group.

The conditional expression (4) defines the focal length of the secondlens group relative to the focal length of the third lens group. Thevariable magnification optical system according to the first embodimentof the present invention is capable of correcting superbly sphericalaberration upon focusing on a closely distant object in the telephotoend state and curvature of field in the wide-angle end state, bysatisfying the conditional expression (4).

When the value of (−f2)/f3 of the conditional expression (4) of thevariable magnification optical system according to the first embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the upper limitvalue of the conditional expression (4) to 0.36.

On the other hand, when the value of (−f2)/f3 of the conditionalexpression (4) of the variable magnification optical system according tothe first embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the second lens groupincreases. Thus, it becomes difficult to correct curvature of field inthe wide-angle end state, so that it is not desirable. Meanwhile, inorder to attain the advantageous effect of the present application moresurely, it is more preferable to set the lower limit value of theconditional expression (4) to 0.15.

In the variable magnification optical system according to the firstembodiment of the present application, it is preferable that thefollowing conditional expression (5) is satisfied:0.42<f3/fR<0.80  (5)where f3 denotes the focal length of the third lens group, and fRdenotes a focal length of the rear lens group in the wide-angle endstate.

The conditional expression (5) defines the focal length of the rear lensgroup in the wide-angle end state relative to the focal length of thethird lens group. Incidentally, in a case where the rear lens group iscomposed of a plurality of lens groups, fR denotes a composite focallength of the plurality of lens groups. With satisfying the conditionalexpression (5), the variable magnification optical system according tothe first embodiment of the present invention is capable of correctingsuperbly spherical aberration upon focusing on a closely distant objectin the telephoto end state and eccentric coma aberration upon conductingthe vibration reduction.

When the value of f3/fR of the conditional expression (5) of thevariable magnification optical system according to the first embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (5) to 1.00.

On the other hand, when the value of f3/fR of the conditional expression(5) of the variable magnification optical system according to the firstembodiment of the present application is equal to or falls below thelower limit, eccentric coma aberration is generated upon conducting thevibration reduction, so that it is not preferable. Meanwhile, in orderto attain the advantageous effect of the present application moresurely, it is more preferable to set the lower limit value of theconditional expression (5) to 0.40.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is preferable that thevibration reduction lens group is composed of a cemented lensconstructed by a positive lens cemented with a negative lens. By thisconfiguration, eccentric coma aberration generated upon conducting thevibration reduction can be corrected superbly.

In the variable magnification optical system according to the firstembodiment of the present application, it is preferable that the firstlens group has a negative lens that satisfies the following conditionalexpression (6):1.90<nd1  (6)where nd1 denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe negative lens in the first lens group.

The conditional expression (6) defines refractive index at d-line(wavelength λ=587.6 nm) of the negative lens in the first lens group.With satisfying the conditional expression (6), the variablemagnification optical system according to the first embodiment of thepresent invention is capable of correcting superbly spherical aberrationin the telephoto end state.

When the value of nd1 of the conditional expression (6) of the variablemagnification optical system according to the first embodiment of thepresent application is equal to or falls below the lower limit, itbecomes difficult to correct spherical aberration in the telephoto endstate, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the lower limit valueof the conditional expression (6) to 1.92.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is preferable that, uponzooming from the wide-angle end state to the telephoto end state, thesecond lens group is moved in the direction of the optical axis. Withtaking such a configuration, curvature of field can be correctedsuperbly.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is preferable that, uponzooming from the wide-angle end state to the telephoto end state, thethird lens group is moved in the direction of the optical axis. Withtaking such a configuration, spherical aberration can be correctedsuperbly.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is preferable that, uponzooming from the wide-angle end state to the telephoto end state, thefirst lens group is moved in the direction of the optical axis. Withtaking such a configuration, higher zoom ratio can be attained.

The optical apparatus of the present application, is characterized inthe provision of the variable magnification optical system according tothe first embodiment having the above described configuration. Owing tothis, an optical apparatus having high zoom ratio, being downsized andhaving superb optical performance, can be realized.

The method for manufacturing the variable magnification optical systemaccording to the first embodiment of the present application is a methodfor manufacturing a variable magnification optical system comprising, inorder from an object side: a first lens group having positive refractivepower; a second lens group having negative refractive power; an aperturestop; a third lens group having positive refractive power; and a rearlens group;

the method being characterized in comprising the steps of:

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, at least the rear lens group is moved toward theobject side; and a distance between the first lens group and the secondlens group, a distance between the second lens group and the third lensgroup, and a distance between the third lens group and the rear lensgroup being varied;

constructing such that upon focusing on from an infinitely distantobject to a close distant object, the third lens group as a whole ismoved in the direction of the optical axis;

constructing such that at least a portion of the rear lens group ismoved as a vibration reduction lens group so as to have a component in adirection perpendicular to the optical axis; and

constructing the vibration reduction lens group to have negativerefractive power.

By such a method, it is possible to manufacture a magnification variableoptical system that has high zoom ratio, is downsized and has superboptical performance.

Next, the variable magnification optical system, the optical apparatusand the method for manufacturing the variable magnification opticalsystem according to the second embodiment of the present application isexplained below.

The variable magnification optical system according to the secondembodiment of the present application comprises, in order from an objectside: a first lens group having positive refractive power; a second lensgroup having negative refractive power; a third lens group havingpositive refractive power and a rear lens group;

upon zooming from a wide-angle end state to a telephoto end state, atleast the first lens group and the rear lens group being moved toward anobject side, and a distance between the first lens group and the secondlens group, a distance between the second lens group and the third lensgroup and a distance between the third lens group and the rear lensgroup being varied;

upon focusing on from an infinitely distant object to a closely distantobject, the third lens group as a whole being moved in the direction ofthe optical axis;

at least a portion of the rear lens group being moved as a vibrationreduction lens group to have a component in a direction perpendicular tothe optical axis;

the vibration reduction lens group having negative refractive power; and

the following conditional expression (3) being satisfied:0.20<(−fVR)/f3<1.20  (3)where fVR denotes a focal length of the vibration reduction lens group,and f3 denotes a focal length of the third lens group.

In the variable magnification optical system according to the secondembodiment of the present application, upon focusing on from aninfinitely distant object to a closely distant object, the third lensgroup as a whole is moved in the direction of the optical axis. Due tosuch a configuration, variation in curvature of field upon focusing aclosely distant object can be preferably suppressed.

In the variable magnification optical system according to the secondembodiment of the present application, at least a portion that is aportion of the rear lens group is moved as a vibration reduction lensgroup to have a component in a direction perpendicular to the opticalaxis, and the vibration reduction lens group has negative refractivepower. Due to such configuration, image blur upon camera shake beingcaused can be corrected, that is, vibration reduction can be effected.Further more, since vibration reduction can be conducted by downsizedlens group, the vibration reduction mechanism can be downsized and madesmall in weight, so that the lens barrel can be downsized preferably.

The conditional expression (3) defines a focal length of the vibrationreduction lens group relative to the focal length of the third lensgroup. The variable magnification optical system according to the secondembodiment of the present application is capable of correcting superblyspherical aberration upon focusing on a closely distant object in thetelephoto end state and eccentric coma aberration upon conducting thevibration reduction.

When the value of (−fVR)/f3 of the conditional expression (3) of thevariable magnification optical system according to the second embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (3) to 1.00.

On the other hand, when the value of (−fVR)/f3 of the conditionalexpression (3) of the variable magnification optical system according tothe second embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the vibration reduction lensgroup increases. Thus, eccentric coma aberration is generated uponconducting the vibration reduction, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (3) to 0.40.

Due to the above configuration, a variable magnification optical systemthat has high zoom ratio, is downsized and has superb opticalperformance, can be realized.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is preferable that thefollowing conditional expression (4) is satisfied:0.10<(−f2)/f3<0.38  (4)where f2 denotes the focal length of the second lens group, and f3denotes the focal length of the third lens group.

The conditional expression (4) defines the focal length of the secondlens group relative to the focal length of the third lens group. Thevariable magnification optical system according to the second embodimentof the present application is capable of correcting superbly sphericalaberration upon focusing on a closely distant object in the telephotoend state and curvature of field in the wide-angle end state.

When the value of (−f2)/f3 of the conditional expression (4) of thevariable magnification optical system according to the second embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the upper limitvalue of the conditional expression (4) to 0.36.

On the other hand, when the value of (−f2)/f3 of the conditionalexpression (4) of the variable magnification optical system according tothe second embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the second lens groupincreases. Thus, it becomes difficult to correct curvature of field inthe wide-angle end state, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (4) to 0.15.

In the variable magnification optical system according to the secondembodiment of the present application, it is preferable that thefollowing conditional expression (1) is satisfied:0.60<f1/f3<2.60  (1)where f1 denotes a focal length of the first lens group, and f3 denotesa focal length of the third lens group.

The conditional expression (1) defines the focal length of the firstlens group relative to the focal length of the third lens group. Withsatisfying the conditional expression (1), the variable magnificationoptical system according to the second embodiment of the presentapplication is capable of correcting superbly spherical aberration uponfocusing on a closely distant object in the telephoto end state andspherical aberration in the telephoto end state.

When the value of f1/f3 of the conditional expression (1) of thevariable magnification optical system according to the second embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the upper limitvalue of the conditional expression (1) to 2.50.

On the other hand, when the value of f1/f3 of the conditional expression(1) of the variable magnification optical system according to the secondembodiment of the present application is equal to or falls below thelower limit, refractive power of the first lens group increases. Thus,spherical aberration is generated in the telephoto end state, so that itis not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (1) to 0.40.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is preferable that thefollowing conditional expression (2) is satisfied:5.00<f1/(−f2)<10.00  (2)where f1 denotes the focal length of the first lens group, and f2denotes a focal length of the second lens group.

The conditional expression (2) defines the focal length of the firstlens group relative to the focal length of the second lens group. Withsatisfying the conditional expression (2), the variable magnificationoptical system according to the second embodiment of the presentinvention is capable of correcting superbly curvature of field in thewide-angle end state and spherical aberration in the telephoto endstate.

When the value of f1/(−f2) of the conditional expression (2) of thevariable magnification optical system according to the second embodimentof the present application is equal to or exceeds the upper limit,refractive power of the second lens group becomes large, and thereby itbecomes difficult to correct curvature of field in the wide-angle endstate. It is not preferable. Meanwhile, in order to attain theadvantageous effect of the present application more surely, it ispreferable to set the upper limit value of the conditional expression(2) to 8.00.

On the other hand, when the value of f1/(−f2) of the conditionalexpression (2) of the variable magnification optical system according tothe second embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the first lens group becomeslarge. Thus, spherical aberration is generated in the telephoto endstate, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (2) to 6.00.

In the variable magnification optical system according to the secondembodiment of the present application, it is preferable that thefollowing conditional expression (5) is satisfied:0.42<f3/fR<0.80  (5)where f3 denotes the focal length of the third lens group, and fRdenotes a focal length of the rear lens group in the wide-angle endstate.

The conditional expression (5) defines the focal length of the rear lensgroup in the wide-angle end state relative to the focal length of thethird lens group. Incidentally, in a case where the rear lens group iscomposed of a plurality of lens groups, fR denotes a composite focallength of the plurality of lens groups. With satisfying the conditionalexpression (5), the variable magnification optical system according tothe second embodiment of the present application is capable ofcorrecting superbly spherical aberration upon focusing on a closelydistant object in the telephoto end state and eccentric coma aberrationupon conducting the vibration reduction.

When the value of f3/fR of the conditional expression (5) of thevariable magnification optical system according to the second embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the upper limitvalue of the conditional expression (5) to 1.00.

On the other hand, when the value of f3/fR of the conditional expression(5) of the variable magnification optical system according to the secondembodiment of the present application is equal to or falls below thelower limit, refractive power of the rear lens group becomes large.Owing to this, eccentric coma aberration is generated upon conductingthe vibration reduction, so that it is not preferable. Meanwhile, inorder to attain the advantageous effect of the present application moresurely, it is more preferable to set the lower limit value of theconditional expression (5) to 0.40.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is preferable that thevibration reduction lens group is composed of a cemented lensconstructed by a positive lens cemented with a negative lens. By thisconfiguration, eccentric coma aberration generated upon conducting thevibration reduction can be corrected superbly.

In the variable magnification optical system according to the secondembodiment of the present application, it is preferable that the firstlens group has a negative lens that satisfies the following conditionalexpression (6):1.90<nd1  (6)where nd1 denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe negative lens in the first lens group.

The conditional expression (6) defines refractive index at d-line(wavelength λ=587.6 nm) of the negative lens in the first lens group.With satisfying the conditional expression (6), the variablemagnification optical system according to the second embodiment of thepresent invention is capable of correcting superbly spherical aberrationin the telephoto end state.

When the value of nd1 of the conditional expression (6) of the variablemagnification optical system according to the second embodiment of thepresent application is equal to or falls below the lower limit, itbecomes difficult to correct spherical aberration in the telephoto endstate, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (6) to 1.92.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is preferable that,upon zooming from the wide-angle end state to the telephoto end state,the second lens group is moved in the direction of the optical axis.With taking such a configuration, curvature of field can be correctedsuperbly.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is preferable that,upon zooming from the wide-angle end state to the telephoto end state,the third lens group is moved in the direction of the optical axis. Withtaking such a configuration, spherical aberration can be correctedsuperbly.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is preferable that,upon zooming from the wide-angle end state to the telephoto end state,the first lens group is moved in the direction of the optical axis. Withtaking such a configuration, higher zoom ratio can be attained.

The optical apparatus of the present application, is characterized inthe provision of the variable magnification optical system according tothe second embodiment having the above described configuration. Owing tothis, an optical apparatus having high zoom ratio, being downsized andhaving superb optical performance, can be realized.

The method for manufacturing the variable magnification optical systemaccording to the second embodiment of the present application is amethod for manufacturing a variable magnification optical systemcomprising, in order from an object side: a first lens group havingpositive refractive power; a second lens group having negativerefractive power; a third lens group having positive refractive power;and a rear lens group, and being characterized in comprising the stepsof:

-   -   constructing such that, upon zooming from a wide-angle end state        to a telephoto end state, at least the first lens group and the        rear lens group are moved toward the object side; and a distance        between the first lens group and the second lens group, a        distance between the second lens group and the third lens group,        and a distance between the third lens group and the rear lens        group are varied;    -   constructing such that, upon focusing on from an infinitely        distant object to a closely distant object, the third lens group        as a whole is moved in the direction of the optical axis,    -   constructing such that at least a portion of the rear lens group        is moved as a vibration reduction lens group so as to have a        component in a direction perpendicular to the optical axis;    -   constructing the vibration reduction lens group to have negative        refractive power; and    -   constructing such that the third lens group and the rear lens        group satisfy the following conditional expression (3):        0.20<(−fVR)/f3<1.20  (3)        where fVR denotes a focal length of the vibration reduction lens        group, and f3 denotes a focal length of the third lens group.

By such a method, it is possible to manufacture a variable magnificationoptical system that has high zoom ratio, is downsized and has superboptical performance.

Next, the variable magnification optical system, the optical apparatusand the method for manufacturing the variable magnification opticalsystem according to the third embodiment of the present application isexplained below.

The variable magnification optical system according to the thirdembodiment of the present application comprises, in order from an objectside: a first lens group having positive refractive power; a second lensgroup having negative refractive power; an aperture stop; a third lensgroup having positive refractive power and a rear lens group, the thirdlens group being composed of a cemented lens constructed by a positivelens cemented with a negative lens;

upon zooming from a wide-angle end state to a telephoto end state, atleast the rear lens group being moved toward an object side, and adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group and adistance between the third lens group and the rear lens group beingvaried; and

upon focusing on from an infinitely distant object to a closely distantobject, the third lens group as a whole being moved in the direction ofthe optical axis.

In the variable magnification optical system according to the thirdembodiment of the present application, focusing on from an infinitelydistant object to a closely distant object, is carried out by moving, asa whole in the direction of the optical axis, the third lens group thatis disposed in the neighborhood of the aperture stop. Due to such aconfiguration, variation in curvature of field upon focusing on aclosely distant object can be preferably suppressed. Moreover, the thirdlens group is composed of a cemented lens constructed by a positive lenscemented with a negative lens, and thereby variation in sphericalaberration upon focusing on the closely distant object as well asvariation in longitudinal chromatic aberration can be suppressed, sothat it is preferable.

By such configuration, a variable magnification optical system that hashigh zoom ratio, is downsized and has superb optical performance, can berealized.

In the variable magnification optical system according to the thirdembodiment of the present application, it is preferable that thefollowing conditional expression (5) is satisfied:0.42<f3/fR<0.80  (5)where f3 denotes the focal length of the third lens group, and fRdenotes a focal length of the rear lens group in the wide-angle endstate.

The conditional expression (5) defines the focal length of the rear lensgroup in the wide-angle end state relative to the focal length of thethird lens group. Incidentally, in a case where the rear lens group iscomposed of a plurality of lens groups, fR denotes a composite focallength of the plurality of lens groups. With satisfying the conditionalexpression (5), the variable magnification optical system according tothe third embodiment of the present invention is capable of correctingsuperbly spherical aberration upon focusing on a closely distant objectin the telephoto end state. Further, in a case where the variablemagnification optical system according to the third embodiment of thepresent application is configured to carry out vibration reduction, itis possible to correct superbly eccentric coma aberration uponconducting the vibration reduction.

When the value of f3/fR of the conditional expression (5) of thevariable magnification optical system according to the third embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the upper limitvalue of the conditional expression (5) to 1.00.

On the other hand, when the value of f3/fR of the conditional expression(5) of the variable magnification optical system according to the thirdembodiment of the present application is equal to or falls below thelower limit, refractive power of the rear lens group becomes large.Owing to this, in the case where the variable magnification opticalsystem according to the third embodiment of the present invention isconfigured to conduct the vibration reduction, eccentric coma aberrationis generated upon conducting the vibration reduction, so that it is notpreferable. Meanwhile, in order to attain the advantageous effect of thepresent application more surely, it is more preferable to set the lowerlimit value of the conditional expression (5) to 0.40.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is preferable that thefollowing conditional expression (2) is satisfied:5.00<f1/(−f2)<10.00  (2)where f1 denotes a focal length of the first lens group, and f2 denotesa focal length of the second lens group.

The conditional expression (2) defines the focal length of the firstlens group relative to the focal length of the second lens group. Withsatisfying the conditional expression (2), the variable magnificationoptical system according to the third embodiment of the presentapplication is capable of correcting superbly curvature of field in thewide-angle end state and spherical aberration in the telephoto endstate.

When the value of f1/(−f2) of the conditional expression (2) of thevariable magnification optical system according to the third embodimentof the present application is equal to or exceeds the upper limit,refractive power of the second lens group becomes large, and it becomesdifficult to correct curvature of field in the wide-angle end state. Itis not preferable. Meanwhile, in order to attain the advantageous effectof the present application more surely, it is preferable to set theupper limit value of the conditional expression (2) to 8.00.

On the other hand, when the value of f1/(−f2) of the conditionalexpression (2) of the variable magnification optical system according tothe third embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the first lens group becomeslarge. Thus, spherical aberration is generated in the telephoto endstate, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (2) to 6.00.

In the variable magnification optical system according to the thirdembodiment of the present application, it is preferable that thefollowing conditional expression (1) is satisfied:0.60<f1/f3<2.60  (1)where f1 denotes the focal length of the first lens group, and f3denotes a focal length of the third lens group.

The conditional expression (1) defines the focal length of the firstlens group relative to the focal length of the third lens group. Withsatisfying the conditional expression (1), the variable magnificationoptical system according to the third embodiment of the presentinvention is capable of correcting superbly spherical aberration uponfocusing on a closely distant object in the telephoto end state andspherical aberration in the telephoto end state.

When the value of f1/f3 of the conditional expression (1) of thevariable magnification optical system according to the third embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (1) to 2.50.

On the other hand, when the value of f1/f3 of the conditional expression(1) of the variable magnification optical system according to the thirdembodiment of the present application is equal to or falls below thelower limit, refractive power of the first lens group increases. Thus,spherical aberration is generated in the telephoto end state, so that itis not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the lower limit valueof the conditional expression (1) to 0.40.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is preferable that thefollowing conditional expression (4) is satisfied:0.10<(−f2)/f3<0.38  (4)where f2 denotes the focal length of the second lens group, and f3denotes the focal length of the third lens group.

The conditional expression (4) defines the focal length of the secondlens group relative to the focal length of the third lens group. Thevariable magnification optical system according to the third embodimentof the present invention is capable of correcting superbly sphericalaberration upon focusing on a closely distant object in the telephotoend state and curvature of field in the wide-angle end state, bysatisfying the conditional expression (4).

When the value of (−f2)/f3 of the conditional expression (4) of thevariable magnification optical system according to the third embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the upper limitvalue of the conditional expression (4) to 0.36.

On the other hand, when the value of (−f2)/f3 of the conditionalexpression (4) of the variable magnification optical system according tothe third embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the second lens groupincreases. Thus, it becomes difficult to correct curvature of field inthe wide-angle end state, so that it is not desirable. Meanwhile, inorder to attain the advantageous effect of the present application moresurely, it is more preferable to set the lower limit value of theconditional expression (4) to 0.15.

In the variable magnification optical system according to the thirdembodiment of the present application, it is preferable that the firstlens group has a negative lens that satisfies the following conditionalexpression (6):1.90<nd1  (6)where nd1 denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe negative lens in the first lens group.

The conditional expression (6) defines refractive index at d-line(wavelength λ=587.6 nm) of the negative lens in the first lens group.With satisfying the conditional expression (6), the variablemagnification optical system according to the third embodiment of thepresent invention is capable of correcting superbly spherical aberrationin the telephoto end state.

When the value of nd1 of the conditional expression (6) of the variablemagnification optical system according to the third embodiment of thepresent application is equal to or falls below the lower limit, itbecomes difficult to correct spherical aberration in the telephoto endstate, so that it is not desirable.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the lower limit valueof the conditional expression (6) to 1.92.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is preferable that alens that is at least a portion of the rear lens group is moved to havea component in a direction perpendicular to the optical axis, and thevibration reduction lens has negative refractive power. By suchconfiguration, it is possible to correct image blur upon generatingcamera shake, that is, to conduct vibration reduction. Moreover, thevibration reduction can be conducted by a lens group having smalldiameter, so the vibration reduction mechanism can be downsized andsmall in weight. Thus, a lens barrel can be downsized. This ispreferable.

Furthermore, in the variable magnification optical system according tothe third embodiment of the present application, it is preferable thatthe vibration reduction lens group is constructed by a cemented lenscomposed of a positive lens and a negative lens. Due to suchconfiguration, eccentric coma aberration upon conducting the vibrationreduction can be corrected excellently.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is preferable that thefollowing conditional expression (3) is satisfied:0.20<(−fVR)/f3<1.20  (3)where fVR denotes a focal length of the vibration reduction lens group,and f3 denotes the focal length of the third lens group.

The conditional expression (3) defines the focal length of the vibrationreduction lens group relative to the focal length of the third lensgroup. With satisfying the conditional expression (3), the variablemagnification optical system according to the third embodiment of thepresent invention is capable of correcting superbly spherical aberrationupon focusing on a closely distant object in the telephoto end state andeccentric coma aberration upon conducting the vibration reduction.

When the value of (−fVR)/f3 of the conditional expression (3) of thevariable magnification optical system according to the third embodimentof the present application is equal to or exceeds the upper limit,refractive power of the third lens group becomes large, and it becomesdifficult to correct spherical aberration upon focusing on the closelydistant object in the telephoto end state. It is not preferable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (3) to 1.00.

On the other hand, when the value of (−fVR)/f3 of the conditionalexpression (3) of the variable magnification optical system according tothe third embodiment of the present application is equal to or fallsbelow the lower limit, refractive power of the vibration reduction lensgroup increases. Thus, eccentric coma aberration is generated uponconducting the vibration reduction, so that it is not desirable.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the lower limit valueof the conditional expression (3) to 0.40.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is preferable that, uponzooming from the wide-angle end state to the telephoto end state, thesecond lens group is moved in the direction of the optical axis. Withtaking such a configuration, curvature of field can be correctedsuperbly.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is preferable that, uponzooming from the wide-angle end state to the telephoto end state, thethird lens group is moved in the direction of the optical axis. Withtaking such a configuration, spherical aberration can be correctedsuperbly.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is preferable that, uponzooming from the wide-angle end state to the telephoto end state, thefirst lens group is moved in the direction of the optical axis. Withtaking such a configuration, higher zoom ratio can be attained.

The optical apparatus of the present application, is characterized inthe provision of the variable magnification optical system according tothe third embodiment having the above described configuration. Owing tothis, an optical apparatus having high zoom ratio, being downsized andhaving superb optical performance, can be realized.

The method for manufacturing the variable magnification optical systemaccording to the third embodiment of the present application is a methodfor manufacturing a variable magnification optical system comprising, inorder from an object side: a first lens group having positive refractivepower; a second lens group having negative refractive power; an aperturestop; a third lens group having positive refractive power; and a rearlens group, and being characterized in comprising the steps of:

-   -   constructing such that the third lens group is composed of a        cemented lens constructed by a positive lens cemented with a        negative lens;    -   constructing such that, upon zooming from a wide-angle end state        to a telephoto end state, at least the rear lens group is moved        toward the object side; and a distance between the first lens        group and the second lens group, a distance between the second        lens group and the third lens group, and a distance between the        third lens group and the rear lens group are varied;    -   constructing such that upon focusing on from an infinitely        distant object to a closely distant object, the third lens group        as a whole is moved in the direction of the optical axis.

By such a method, it is possible to manufacture a variable magnificationoptical system that has high zoom ratio, is downsized and has superboptical performance.

The variable magnification optical system, the optical apparatus and themethod for manufacturing the variable magnification optical systemaccording to the fourth embodiment of the present application isexplained below.

The variable magnification optical system according to the fourthembodiment of the present application comprises, in order from an objectside: a first lens group having positive refractive power; a second lensgroup having negative refractive power; a third lens group havingpositive refractive power; and a fourth lens group having positiverefractive power;

upon zooming from a wide-angle end state to a telephoto end state, adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group, and adistance between the third lens group and the fourth lens group arevaried.

By such a configuration, the variable magnification optical systemaccording to the fourth embodiment of the present application canrealize zooming from a wide-angle end state to a telephoto end state,and variation in distortion caused upon zooming can be suppressed.

Further, the variable magnification optical system according to thefourth embodiment of the present application is characterized in havingat least one lens that satisfies the following conditional expressions(7) and (8):1.928<ndh  (7)28.60<νdh  (8)where ndh denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe lens, and νdh denotes Abbe number at d-line (wavelength λ=587.6 nm)of the lens.

The conditional expression (7) defines optimal refractive index of thelens. With satisfying the conditional expression (7), the variablemagnification optical system according to the fourth embodiment of thepresent application is capable of suppressing variation in sphericalaberration as well as variation in astigmatism upon zooming, while beingdownsized.

When the value of ndh of the conditional expression (7) of the variablemagnification optical system according to the fourth embodiment of thepresent application is equal to or falls below the lower limit, itbecomes difficult to suppress variation in spherical aberration as wellas variation in astigmatism upon zooming, so that high opticalperformance cannot become realized. Meanwhile, in order to attain theadvantageous effect of the present application more surely, it is morepreferable to set the lower limit value of the conditional expression(7) to 1.940.

In order to attain the advantageous effect of the present applicationmore surely, it is more preferable to set the upper limit value of theconditional expression (7) to 2.800. If the value of ndh is made smallerthan 2.800, it is possible to ensure sufficiently transmittance ofvisible light rays for material of the lens.

The conditional expression (8) defines optimal Abbe number of the lens.With satisfying the conditional expression (8), the variablemagnification optical system according to the fourth embodiment of thepresent application is capable of suppressing variation in longitudinalchromatic aberration as well as variation in lateral chromaticaberration upon zooming, while being downsized.

When the value of νdh of the conditional expression (8) of the variablemagnification optical system according to the fourth embodiment of thepresent application is equal to or falls below the lower limit, itbecomes difficult to suppress variation in longitudinal chromaticaberration as well as variation in lateral chromatic aberration uponzooming, so that high optical performance cannot become realized.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (8) to 29.00. In order to attain theadvantageous effect of the present application further more surely, itis further more preferable to set the lower limit value of theconditional expression (8) to 32.00.

In order to attain the advantageous effect of the present applicationmore surely, it is more preferable to set the upper limit value of theconditional expression (8) to 50.00. If the value of νdh is made smallerthan 50.00, it is possible to suppress variation in longitudinalchromatic aberration and variation in lateral chromatic aberration whichare generated at other lenses than the said lens upon zooming, andaccordingly high optical performance can be realized.

Due to the above described configuration, a variable magnificationoptical system that is downsized and has high optical performance, canbe realized.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the firstlens group has at least one said lens. By such configuration, it ispossible to suppress respective variations in spherical aberration,astigmatism, longitudinal chromatic aberration and lateral chromaticaberration which are generated at the first lens group upon zooming.

Further, in the variable magnification optical system according to thefourth embodiment of the present application, it is preferable that thefollowing conditional expression (9) is satisfied:5.50<f1/(−f2)<15.00  (9)where f1 denotes a focal length of the first lens group, and f2 denotesa focal length of the second lens group.

The conditional expression (9) defines the focal length of the firstlens group relative to the focal length of the second lens group. Withsatisfying the conditional expression (9), the variable magnificationoptical system according to the fourth embodiment of the presentinvention is capable of suppressing variation in astigmatism uponzooming while maintaining high zoom ratio.

When the value of f1/(−f2) of the conditional expression (9) of thevariable magnification optical system according to the fourth embodimentof the present application is equal to or falls below the lower limit,astigmatism is generated largely in the wide-angle end state, so that itbecomes not possible to attain high optical performance. Meanwhile, inorder to attain the advantageous effect of the present application moresurely, it is preferable to set the lower limit value of the conditionalexpression (9) to 5.90.

On the other hand, when the value of f1/(−f2) of the conditionalexpression (9) of the variable magnification optical system according tothe fourth embodiment of the present application is equal to or exceedsthe upper limit, it becomes difficult to suppress variation inastigmatism generated at the second lens group upon zooming. Meanwhile,in order to attain the advantageous effect of the present applicationmore surely, it is more preferable to set the upper limit value of theconditional expression (9) to 11.50. Further, in order to attain theadvantageous effect of the present application more surely, it is morepreferable to set the upper limit value of the conditional expression(9) to 10.20.

Due to the above described configuration, a variable magnificationoptical system that is downsized and has high optical performance, canbe realized.

Further, in the variable magnification optical system according to thefourth embodiment of the present application, it is preferable that thefollowing conditional expression (10) is satisfied:0.220<(−f2)/f3<0.530  (10)where f2 denotes the focal length of the second lens group, and f3denotes a focal length of the third lens group.

The conditional expression (10) defines a proper range of a ratio of thefocal length of the second lens group to the focal length of the thirdlens group. The variable magnification optical system according to thefourth embodiment of the present invention is capable of suppressingvariation in spherical aberration and variation in astigmatism uponzooming, while maintaining high zoom ratio, by satisfying theconditional expression (10).

When the value of (−f2)/f3 of the conditional expression (10) of thevariable magnification optical system according to the fourth embodimentof the present application is equal to or falls below the lower limit,it becomes difficult to suppress variation in astigmatism generated atthe second lens group upon zooming. Meanwhile, in order to attain theadvantageous effect of the present application more surely, it is morepreferable to set the lower limit value of the conditional expression(10) to 0.270.

On the other hand, when the value of (−f2)/f3 of the conditionalexpression (10) of the variable magnification optical system accordingto the fourth embodiment of the present application is equal to orexceeds the upper limit, it becomes difficult to suppress variation inspherical aberration generated at the third lens group upon zooming.Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the upper limitvalue of the conditional expression (10) to 0.490. Furthermore, it ismore preferable to set the upper limit value of the conditionalexpression (10) to 0.450.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the firstlens group has at least one lens that satisfies the followingconditional expression (11):0.450<|fh/f1|<1.400  (11)where fh denotes a focal length of the lens in the first lens group, andf1 denotes the focal length of the first lens group.

The conditional expression (11) defines a proper focal length range ofthe said lens in the first lens group. Meanwhile, when the said lens iscemented with other lens, fh denotes the focal length of the said lensalone. In the variable magnification optical system according to thefourth embodiment of the present application, it is preferable that thefirst lens group has at least one said lens. The variable magnificationoptical system according to the fourth embodiment of the presentapplication can suppress respective variations in spherical aberration,astigmatism, longitudinal chromatic aberration and lateral chromaticaberration which are generated upon zooming, by satisfying theconditional expression (11).

Here, with respect to the conditional expression (11), two cases wherethe said lens has positive refractive power and where the said lens hasnegative refractive power will be separately explained.

In the case where the said lens has positive refractive power, when thevalue of |fh/f1| of the conditional expression (11) of the variablemagnification optical system according to the fourth embodiment of thepresent application is equal to or falls below the lower limit, itbecomes difficult to suppress variation in longitudinal chromaticaberration and variation in lateral chromatic aberration generated atthe said lens upon zooming, so that high optical performance can not berealized. On the other hand, when the value of |fh/f1| of theconditional expression (11) of the variable magnification optical systemaccording to the fourth embodiment of the present application is equalto or exceeds the upper limit, it becomes difficult to suppress positivespherical aberration generated at the second lens group in the telephotoend state, thereby it becoming not possible to realize high opticalperformance.

In the case where the said lens has negative refractive power, when thevalue of |fh/f1| of the conditional expression (11) of the variablemagnification optical system according to the fourth embodiment of thepresent application is equal to or falls below the lower limit, itbecomes difficult to suppress variation in astigmatism generated at thesaid lens upon zooming, so that high optical performance can not berealized. On the other hand, when the value of |fh/f1| of theconditional expression (11) of the variable magnification optical systemaccording to the fourth embodiment of the present application is equalto or exceeds the upper limit, it becomes difficult to suppressvariation in longitudinal chromatic aberration and variation in lateralchromatic aberration which are generated at other lenses than the saidlens upon zooming, and accordingly high optical performance can not berealized.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is more preferable to set the lower limitvalue of the conditional expression (11) to 0.620. Further, it is morepreferable to set the upper limit value of the conditional expression(11) to 1.290.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the fourthlens group has at least one said lens. With this configuration, it ispossible to suppress, from the wide-angle end state to the telephoto endstate, respective variations in spherical aberration, astigmatism,longitudinal chromatic aberration and lateral chromatic aberration whichare generated at the fourth lens group.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the secondlens group has at least one said lens. With this configuration, it ispossible to suppress, from the wide-angle end state to the telephoto endstate, respective variations in spherical aberration, astigmatism,longitudinal chromatic aberration and lateral chromatic aberration whichare generated at the second lens group upon zooming.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the thirdlens group has at least one said lens. With this configuration, it ispossible to suppress, from the wide-angle end state to the telephoto endstate, respective variations in spherical aberration, astigmatism,longitudinal chromatic aberration and lateral chromatic aberration whichare generated at the third lens group upon zooming.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the firstlens group has at least one said lens that has negative refractivepower. With this configuration, it is possible to suppress variation inastigmatism, variation in spherical aberration, longitudinal chromaticaberration and particularly variation in secondary chromatic aberration,which are generated at the first lens group upon zooming, thereby itbecoming possible to realize high optical performance.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the fourthlens group has at least one said lens that has negative refractivepower. With this configuration, it is possible to suppress variation inastigmatism, variation in spherical aberration and longitudinalchromatic aberration which are generated at the fourth lens group uponzooming, thereby it becoming possible to realize high opticalperformance.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the fourthlens group has at least one said lens that satisfies the followingconditional expression (12):31.60<νdh4  (12)Where νdh4 denotes Abbe number at d-line (wavelength λ=587.6 nm) of thesaid lens in the fourth lens group.

The conditional expression (12) defines optimal Abbe number of the saidlens in the fourth lens group. With satisfying the conditionalexpression (12), the variable magnification optical system according tothe fourth embodiment of the present invention is capable of suppressinglongitudinal chromatic aberration and lateral chromatic aberration.

When the value of νdh4 of the conditional expression (12) of thevariable magnification optical system according to the fourth embodimentof the present application is equal to or falls below the lower limit,it becomes difficult to suppress longitudinal chromatic aberration andlateral chromatic aberration generated at other lenses than the saidlens, so that high optical performance can not be realized.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the secondlens group has at least one said lens that has negative refractivepower. With this configuration, it is possible to suppress variation inlongitudinal chromatic aberration, lateral chromatic aberration andparticularly secondary chromatic aberration, which are generated at thesecond lens group, thereby it becoming possible to realize high opticalperformance.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the thirdlens group has at least one said lens, has negative refractive power.With this configuration, it is possible to suppress longitudinalchromatic aberration and particularly secondary chromatic aberration,which are generated at the third lens group, thereby it becomingpossible to realize high optical performance.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the firstlens group has at least one positive lens that satisfies the followingconditional expression (13):75.00<νdp1  (13)Where νdp1 denotes Abbe number at d-line (wavelength λ=587.6 nm) of thesaid positive lens in the first lens group.

The conditional expression (13) defines optimal Abbe number of the saidpositive lens in the first lens group. With satisfying the conditionalexpression (13), the variable magnification optical system according tothe fourth embodiment of the present invention is capable of suppressingvariation in longitudinal chromatic aberration and variation in lateralchromatic aberration, upon zooming.

When the value of νdp1 of the conditional expression (13) of thevariable magnification optical system according to the fourth embodimentof the present application is equal to or falls below the lower limit,it becomes difficult to suppress variation in longitudinal chromaticaberration and variation in lateral chromatic aberration, upon zooming,so that high optical performance can not be realized.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (13) to 99.00. If the value of νdp1 in theconditional expression (13) of the variable magnification optical systemaccording to the fourth embodiment of the present application, issmaller than 99.00, it is possible to suppress variation in longitudinalchromatic aberration and variation in lateral chromatic aberration whichare generated at other lenses than the said positive lens upon zooming,so that high optical performance can be realized.

In the variable magnification optical system according to the fourthembodiment of the present application, it is preferable that the fourthlens group has a positive lens that satisfies the following conditionalexpression (14):75.00<νdp4  (14)Where νdp4 denotes Abbe number at d-line (wavelength λ=587.6 nm) of thesaid positive lens in the fourth lens group.

The conditional expression (14) defines optimal Abbe number of the saidpositive lens in the fourth lens group. With satisfying the conditionalexpression (14), the variable magnification optical system according tothe fourth embodiment of the present invention is capable of suppressingvariation in longitudinal chromatic aberration and variation in lateralchromatic aberration, upon zooming.

When the value of νdp4 of the conditional expression (14) of thevariable magnification optical system according to the fourth embodimentof the present application is equal to or falls below the lower limit,it becomes difficult to suppress variation in longitudinal chromaticaberration, upon zooming, so that high optical performance can not berealized.

Meanwhile, in order to attain the advantageous effect of the presentapplication more surely, it is preferable to set the upper limit valueof the conditional expression (14) to 99.00. If the value of νdp4 in theconditional expression (14) of the variable magnification optical systemaccording to the fourth embodiment of the present application, issmaller than 99.00, it is possible to suppress variation in longitudinalchromatic aberration generated at other lenses than the said positivelens, so that high optical performance can be realized.

Further, in the variable magnification optical system according to thefourth embodiment of the present application, it is preferable that,upon zooming from the wide-angle end state to the telephoto end state, adistance between the first lens group and the second lens groupincreases. With such configuration, the focal length of the first lensgroup and the focal length of the second lens group can be made proper.And, spherical aberration and astigmatism generated at each lens can besuppressed, and variation in spherical aberration and variation inastigmatism upon zooming can be suppressed.

Further, in the variable magnification optical system according to thefourth embodiment of the present application, it is preferable that,upon zooming from the wide-angle end state to the telephoto end state, adistance between the second lens group and the third lens groupdecreases. With such configuration, the focal length of the second lensgroup and the focal length of the third lens group can be made proper.And, spherical aberration and astigmatism generated at each lens can besuppressed, and variation in spherical aberration and variation inastigmatism upon zooming can be suppressed.

Further, in the variable magnification optical system according to thefourth embodiment of the present application, it is preferable that,upon zooming from the wide-angle end state to the telephoto end state, adistance between the third lens group and the fourth lens groupincreases. With such configuration, variation in spherical aberrationand variation in astigmatism generated at the third lens group and thefourth lens group upon zooming can be suppressed.

The optical apparatus of the present application, is characterized inthe provision of the variable magnification optical system according tothe fourth embodiment having the above described configuration. Owing tothis, an optical apparatus that is downsized and has high opticalperformance, can be realized.

The method for manufacturing the variable magnification optical systemaccording to the fourth embodiment of the present application is amethod for manufacturing a variable magnification optical systemcomprising, in order from an object side: a first lens group havingpositive refractive power; a second lens group having negativerefractive power; a third lens group having positive refractive power;and a fourth lens group having positive refractive power, and beingcharacterized in comprising the steps of:

constructing such that at least one lens satisfies the followingconditional expressions (7) and (8):1.928<ndh  (7)28.60<νdh  (8)where ndh denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe said lens, and νdh denotes Abbe number at d-line (wavelength λ=587.6nm) of the said lens; and

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group, a distance between the second lens group and thethird lens group, and a distance between the third lens group and thefourth lens group are varied. By such a configuration, it is possible tomanufacture a variable magnification optical system that is downsizedand has high optical performance.

Hereinafter, a variable magnification optical system relating tonumerical examples according to the first to the third embodiments ofthe present application will be explained with reference to theaccompanying drawings. Meanwhile, the first to the third examples arecommon to all of the first to the third embodiments.

First Example

FIGS. 1A, 1B and 1C are sectional views showing a variable magnificationoptical system according to a first example that is common to a first tothird embodiments of the present application, in which FIG. 1A showssectional view in a wide-angle end state, FIG. 1B shows sectional viewin an intermediate focal length state, and FIG. 1C shows sectional viewin a telephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a rear lens group GR having positive refractivepower. The rear lens group GR is composed of, in order from an objectside: a fourth lens group G4 having negative refractive power and afifth lens group G5 having positive refractive power.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a positive meniscus lens L13 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 having a convex surface facing the objectside, a double concave negative lens L22, a double convex positive lensL23 and a negative meniscus lens L24 having a concave surface facing theobject side. The most object side negative meniscus lens L21 in thesecond lens group G2 is an aspherical lens whose object side lenssurface is aspherically shaped.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32. An aperture stop S is disposed at the object side ofthe third lens group G3.

The fourth lens group G4 consists of, in order from the object side, afirst segment lens group G41 having positive refractive power and asecond segment lens group G42 having negative refractive power.

The first segment lens group G41 consists of, in order from the objectside, a cemented lens constructed by a double convex positive lens L41cemented with a negative meniscus lens L42 having a concave surfacefacing the object side.

The second segment lens group G42 consists of, in order from the objectside, a cemented lens constructed by a double concave negative lens L43cemented with a positive meniscus lens L44 having a convex surfacefacing the object side. The most object side negative lens L43 in thesecond segment lens group G42 is an aspherical lens whose object sidesurface is aspherically shaped.

The fifth lens group G5 consists of, in order from the object side, adouble convex positive lens L51, and a cemented lens constructed by adouble convex positive lens L52 cemented with a negative meniscus lensL53 having a concave surface facing the object side. The most objectside positive lens L51 in the fifth lens group G5 is an aspherical lenswhose object side surface is aspherically shaped.

In the variable magnification optical system according to the presentexample, zooming from the wide-angle end state to the telephoto endstate, is conducted by moving the first lens group G1, the third lensgroup G3, the fourth lens group G4 and the fifth lens group G5 along theoptical axis toward the object side and moving the second lens group G2and the aperture stop S along the optical axis such that a distancebetween the first lens group G1 and the second lens group G2 isincreased, a distance between the second lens group G2 and the thirdlens group G3 is decreased, a distance between the third lens group G3and the fourth lens group G4 is varied, and a distance between thefourth lens group G4 and the fifth lens group G5 is decreased.

In the variable magnification optical system according to the presentexample, the third group G3 as a whole is moved along the optical axistoward the image side, thereby conducting focusing from an infinitelydistant object to a close distant object.

In the variable magnification optical system according to the presentexample, only the second segment lens group G42 in the fourth lens groupG4 is moved, as a vibration reduction lens group, to have a component ina direction perpendicular to the optical axis, thereby conductingvibration reduction.

It is noted that in a lens system having a focal length f of the wholelens system and a vibration reduction coefficient K, which is a ratio ofa moving amount of an image on the image plane I to a moving amount ofthe vibration reduction lens group upon conducting a vibrationreduction, it is possible to correct rotational camera shake of an angleθ, by moving the vibration reduction lens group by the amount of (f·tanθ)/K perpendicularly to the optical axis.

Accordingly, in the variable magnification optical system according tothe present example, in the wide-angle end state, the vibrationreduction coefficient K is −1.03, and the focal length is 10.30 (mm), sothat the moving amount of the second segment lens group G42 forcorrecting a rotational camera shake of 0.62 degrees is −0.11 (mm). Inthe telephoto end state, the vibration reduction coefficient K is −1.87,and the focal length is 97.00 (mm), so that the moving amount of thesecond segment lens group G42 for correcting a rotational camera shakeof 0.20 degrees is −0.18 (mm).

Table 1 below shows various values of the variable magnification opticalsystem according to the present example.

In table 1, f denotes a focal length, and BF denotes a back focal length(a distance on the optical axis between the most image side lens surfaceand the image plane I).

In [Surface Data], m denotes an order of an optical surface counted fromthe object side, r denotes a radius of curvature, d denotes asurface-to-surface distance (an interval from an n-th surface to an(n+1)-th surface, where n is an integer.), nd denotes refractive indexfor d-line (wavelength λ=587.6 nm) and νd denotes an Abbe number ford-line (wavelength λ=587.6 nm). Further, OP denotes an object surface,and I denotes an image plane. Meanwhile, radius of curvature r=∞ denotesa plane surface. The position of an aspherical surface is expressed byattaching “*” to the surface number, and in the column of the radius ofcurvature, a paraxial radius of curvature is shown.

In [Aspherical Data], with respect to an aspherical surface shown in[Surface Data], an aspherical surface coefficient and a conicalcoefficient are shown in the case where the aspherical surface isexhibited by the following expression:X=(h ² /r)/[1+[1−κ(h ² /r ²)]^(1/2) ]+A4h ⁴ +A6h ⁶ +A8h ⁸ +A10h ¹⁰where h denotes a vertical height from the optical axis, X denotes a sagamount which is a distance along the optical axis from the tangentsurface at the vertex of the aspherical surface to the asphericalsurface at the vertical height from the optical axis, x denotes aconical coefficient, A4, A6, A8 and A10 denote respective asphericalcoefficients, and r denotes a paraxial radius of curvature that is aradius of curvature of a reference sphere. “E−n”, where n is an integer,denotes “×10^(−n)”, for example, “1.234E−05” denotes “1.234×10⁻⁵”. The2nd order aspherical surface coefficient A2 is 0, and omitted in thedescription.

In [Various Data], FNO denotes an f-number, 2ω denotes an angle of view(unit “·”, Y denotes an image height, TL denotes a total length of thevariable magnification optical system, that is, a distance along theoptical axis from the first surface to the image plane I, dn denotes avariable interval between an n-th surface and an (n+1)-th surface. βdenotes a phototaking magnification upon focusing on an object of 0.45mm. Meanwhile, W denotes a wide-angle end state, M denotes anintermediate focal length state, and T denotes a telephoto end state.

In [Lens Group Data], a starting surface ST and focal length of eachlens group are shown.

In [Values for Conditional Expressions], values corresponding torespective conditional expressions are shown.

It is noted, here, that “mm” is generally used for the unit of lengthsuch as the focal length f, the radius of curvature r and the unit forother lengths shown in Table 1. However, since similar opticalperformance can be obtained by an optical system proportionally enlargedor reduced its dimension, the unit is not necessarily to be limited to“mm”.

The explanation of reference symbols in Table 1 described above, is thesame in Tables for the other examples.

TABLE 1 First Example [Surface Data] m r d nd νd OP ∞  1 149.869 1.6001.94967 27.56  2 44.374 6.840 1.49782 82.51  3 −243.506 0.100 1.00000  445.376 5.351 1.86790 41.78  5 311.414  d5 1.00000 *6 89.024 1.2001.83481 42.73  7 8.490 3.758 1.00000  8 −15.726 1.000 1.83481 42.73  9250.000 0.100 1.00000 10 25.275 3.293 1.80809 22.74 11 −17.475 0.5481.00000 12 −12.620 1.000 1.81600 46.59 13 −33.425 d13 1.00000 14 ∞ d141.00000 Aperture Stop S 15 29.168 1.000 1.88904 39.77 16 18.240 3.2071.59313 66.16 17 −26.526 d17 1.00000 18 14.286 3.565 1.49782 82.51 19−21.978 1.000 1.90200 25.23 20 −82.840 2.205 1.00000 *21  −52.307 1.0001.84898 43.01 22 9.141 2.692 1.95000 29.37 23 25.864 d23 1.00000 *24 35.441 3.335 1.58913 61.22 25 −21.319 0.300 1.00000 26 42.310 4.4031.58144 40.98 27 −10.198 1.200 1.95400 33.46 28 −300.472 BF 1.00000 I ∞[Aspherical Surface Data] m κ A4 A6 A8 A10 6 1.00000 3.46E−05 −1.39E−07 −5.60E−11 1.26E−11 21 1.00000 1.74E−06 1.28E−07 −2.64E−09 24 1.00000−1.23E−05  1.47E−07 −5.49E−10 [Various Data] zoom ratio 9.42 W M T f10.30 50.00 97.00 FNO 3.50 5.20 5.60 2ω 79.80 18.04 9.37 Y 8.19 8.198.19 TL 99.26 129.21 139.68 [Upon focusing an infinitely distant object]W M T f 10.30 50.00 97.00 d5 2.000 30.682 41.260 d13 18.534 4.142 2.000d14 3.765 2.963 1.400 d17 3.542 4.343 5.907 d23 8.018 3.307 3.300 BF14.70 35.08 37.11 [Upon focusing on a closely distant object] W M T β−0.025 −0.103 −0.153 d5 2.000 30.682 41.260 d13 18.534 4.142 2.000 d144.216 4.444 5.211 d17 3.090 2.863 2.096 d23 8.018 3.307 3.300 BF 14.7035.08 37.11 [Lens Group Data] ST f G1 1 66.85 G2 6 −9.36 G3 15 27.88 G418 −160.92 G5 24 33.56 GR 18 53.0 [Values for Conditional Expression](1) f1/f3 = 2.40 (2) f1/(−f2) = 7.14 (3) (−fVR)/f3 = 0.85 (4) (−f2)/f3 =0.34 (5) f3/fR = 0.53 (6) nd1 = 1.94967

FIGS. 2A, 2B and 2C are graphs showing various aberrations of thevariable magnification optical system according to the first example ofthe present application upon focusing on an infinitely distant object,in which FIG. 2A is in a wide-angle end state, FIG. 2B is in anintermediate focal length state, and FIG. 2C is in a telephoto endstate.

FIGS. 3A and 3B are graphs showing meridional transverse aberration ofthe variable magnification optical system according to the first exampleupon focusing on an infinitely distant object in the wide-angle endstate with carrying out vibration reduction in which FIG. 3A is for arotational camera shake of 0.62 degrees in the wide-angle end state, andFIG. 3B is for a rotational camera shake of 0.20 degrees in a telephotoend state.

In respective graphs, FNO denotes an f-number, Y denotes an imageheight. In respective graphs, d denotes an aberration curve at d-line(wavelength λ=587.6 nm), and g denotes an aberration curve at g-line(wavelength λ=435.8 nm). In the graph showing astigmatism, a solid lineindicates a sagittal image plane, and a broken line indicates ameridional image plane.

Incidentally, the above-described explanation regarding variousaberration graphs is the same as the other Examples.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state, and also showssuperb optical performance upon carrying out vibration reduction.

Second Example

FIGS. 4A, 4B and 4C are sectional views showing a variable magnificationoptical system according to a second example that is common to the firstto third embodiments of the present application, in which FIG. 4A showssectional view in a wide-angle end state, FIG. 4B shows sectional viewin an intermediate focal length state, and FIG. 4C shows sectional viewin a telephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a rear lens group GR having positive refractivepower. The rear lens group GR is composed of, in order from an objectside: a fourth lens group G4 having negative refractive power and afifth lens group G5 having positive refractive power.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a positive meniscus lens L13 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 having a convex surface facing the objectside, a double concave negative lens L22, a cemented lens constructed bya double convex positive lens L23 and a negative meniscus lens L24having a concave surface facing the object side. The most object sidenegative meniscus lens L21 in the second lens group G2 is an asphericallens whose object side lens surface is aspherically shaped.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32. An aperture stop S is disposed at the object side ofthe third lens group G3.

The fourth lens group G4 consists of, in order from the object side, afirst segment lens group G41 having positive refractive power and asecond segment lens group G42 having negative refractive power.

The first segment lens group G41 consists of, in order from the objectside, a cemented lens constructed by a double convex positive lens L41cemented with a negative meniscus lens L42 having a concave surfacefacing the object side.

The second segment lens group G42 consists of, in order from the objectside, a cemented lens constructed by a double concave negative lens L43cemented with a double convex positive lens L44. The most object sidenegative lens L43 in the second segment lens group G42 is an asphericallens whose object side surface is aspherically shaped.

The fifth lens group G5 consists of, in order from the object side, adouble convex positive lens L51, a cemented lens constructed by a doubleconvex positive lens L52 cemented with a negative meniscus lens L53having a concave surface facing the object side. The most object sidepositive lens L51 in the fifth lens group G5 is an aspherical lens whoseobject side surface is aspherically shaped.

In the variable magnification optical system according to the presentexample, zooming from the wide-angle end state to the telephoto endstate, is conducted by moving the first lens group G1, the third lensgroup G3, the fourth lens group G4 and the fifth lens group G5 along theoptical axis toward the object side and moving the second lens group G2and the aperture stop S along the optical axis such that a distancebetween the first lens group G1 and the second lens group G2 isincreased, a distance between the second lens group G2 and the thirdlens group G3 is decreased, a distance between the third lens group G3and the fourth lens group G4 is varied, and a distance between thefourth lens group G4 and the fifth lens group G5 is decreased.

In the variable magnification optical system according to the presentexample, the third group G3 as a whole is moved along the optical axistoward the image side, thereby conducting focusing from an infinitelydistant object to a close distant object.

In the variable magnification optical system according to the presentexample, only the second segment lens group G42 in the fourth lens groupG4 is moved, as a vibration reduction lens group, to have a component ina direction perpendicular to the optical axis, thereby conductingvibration reduction.

In the variable magnification optical system according to the presentexample, in the wide-angle end state, the vibration reductioncoefficient is −1.43, and the focal length is 10.30 (mm), so that themoving amount of the second segment lens group G42 for correcting arotational camera shake of 0.62 degrees is −0.08 (mm). In the telephotoend state, the vibration reduction coefficient is −2.59, and the focallength is 97.00 (mm), so that the moving amount of the second segmentlens group G42 for correcting a rotational camera shake of 0.20 degreesis −0.13 (mm).

TABLE 2 Second Example [Surface Data] m r d nd νd OP ∞  1 161.271 1.6001.95000 29.37  2 49.424 6.736 1.49782 82.51  3 −163.134 0.100 1.00000  442.661 5.130 1.80400 46.60  5 174.429  d5 1.00000 *6 81.138 1.2001.81600 46.59  7 8.430 3.674 1.00000  8 −20.479 1.000 1.88300 40.76  9120.000 0.100 1.00000 10 20.642 3.336 1.80809 22.74 11 −21.855 1.0001.83481 42.73 12 −2443.660 d12 1.00000 13 ∞ d13 1.00000 Aperture Stop S14 32.818 1.000 1.95400 33.46 15 12.652 3.417 1.75484 52.35 16 −38.178d16 1.00000 17 14.363 4.402 1.49782 82.51 18 −19.407 1.000 1.88087 27.5119 −31.773 2.035 1.00000 *20  −36.627 1.000 1.88300 40.66 21 7.873 2.7501.95000 29.37 22 20.460 d22 1.00000 *23  34.272 3.115 1.61800 63.34 24−25.939 0.100 1.00000 25 29.742 4.552 1.58144 40.98 26 −10.558 1.2001.95400 33.46 27 −228.600 BF 1.00000 I ∞ [Aspherical Surface Data] m κA4 A6 A8 6 1.00000 −2.03E−06 2.60E−08 −4.85E−10 20 1.00000  2.72E−05−6.63E−08  23 1.00000 −9.13E−06 3.14E−08 [Various Data] zoom ratio 9.42W M T f 10.30 50.00 97.00 FNO 3.50 5.20 5.60 2ω 79.80 18.04 9.37 Y 8.198.19 8.19 TL 98.69 127.23 138.71 [Upon focusing an infinitely distantobject] W M T f 10.30 50.00 97.00 d5 2.000 30.607 41.889 d12 18.8653.375 2.000 d13 5.283 4.127 1.400 d16 2.502 3.658 6.385 d22 7.241 3.3023.300 BF 14.35 33.71 35.29 [Upon focusing on a closely distant object] WM T β −0.025 −0.103 −0.152 d5 2.000 30.607 41.889 d12 18.865 3.375 2.000d13 5.785 5.785 5.774 d16 2.000 2.000 2.011 d22 7.241 3.302 3.300 BF14.35 33.71 35.29 [Lens Group Data] ST f G1 1 69.02 G2 6 −10.07 G3 1430.75 G4 17 −167.27 G5 23 28.42 GR 17 46.2 [Values for ConditionalExpression] (1) f1/f3 = 2.24 (2) f1/(−f2) = 6.85 (3) (−fVR)/f3 = 0.51(4) (−f2)/f3 = 0.33 (5) f3/fR = 0.67 (6) nd1 = 1.95000

FIGS. 5A, 5B and 5C are graphs showing various aberrations of thevariable magnification optical system according to the second example ofthe present application upon focusing on an infinitely distant object,in which FIG. 5A is in a wide-angle end state, FIG. 5B is in anintermediate focal length state, and FIG. 5C is in a telephoto endstate.

FIGS. 6A and 6B are graphs showing meridional transverse aberration ofthe variable magnification optical system according to the secondexample upon focusing on an infinitely distant object in the wide-angleend state with carrying out vibration reduction in which FIG. 6A is fora rotational camera shake of 0.62 degrees in the wide-angle end state,and FIG. 6B is for a rotational camera shake of 0.20 degrees in atelephoto end state.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state, and also showssuperb optical performance upon carrying out vibration reduction.

Third Example

FIGS. 7A, 7B and 7C are sectional views showing a variable magnificationoptical system according to a third example that is common to the firstto third embodiments of the present application, in which FIG. 7A showssectional view in a wide-angle end state, FIG. 7B shows sectional viewin an intermediate focal length state, and FIG. 7C shows sectional viewin a telephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a rear lens group GR having positive refractivepower. The rear lens group GR consists of a fourth lens group G4 havingpositive refractive power.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a plano-convex positive lens L13 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 having a convex surface facing the objectside, a negative meniscus lens L22 having a concave surface facing theobject side, a cemented lens constructed by a double convex positivelens L23 and a negative meniscus lens L24 having a concave surfacefacing the object side. The most object side negative meniscus lens L21in the second lens group G2 is an aspherical lens whose object side lenssurface is provided with a resin layer to be formed with an asphericalsurface.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32. An aperture stop S is disposed at the object side ofthe third lens group G3.

The fourth lens group G4 consists of, in order from the object side, afirst segment lens group G41 having positive refractive power, a secondsegment lens group G42 having negative refractive power and a thirdsegment lens group G43 having positive refractive power.

The first segment lens group G41 consists of, in order from the objectside, a cemented lens constructed by a double convex positive lens L401cemented with a negative meniscus lens L402 having a concave surfacefacing the object side.

The second segment lens group G42 consists of, in order from the objectside, a cemented lens constructed by a positive meniscus lens L403cemented with a double concave negative lens L404. The most image sidenegative lens L404 in the second segment lens group G42 is an asphericallens whose image side surface is aspherically shaped.

The third segment lens group G43 consists of, in order from the objectside, a double convex positive lens 405, a cemented lens constructed bya double convex positive lens L406 cemented with a double concavenegative lens L407, a cemented lens constructed by a double convexpositive lens L408 cemented with a negative meniscus lens L409 having aconcave surface facing the object side, and a negative meniscus lenshaving a concave surface facing the object side. The most image sidenegative lens L410 in the third segment lens group G43 is an asphericallens whose image side surface is aspherically shaped.

By the above described configuration, in the variable magnificationoptical system according to the present example, zooming from thewide-angle end state to the telephoto end state, is conducted by movingthe first lens group G1, the third lens group G3 and the fourth lensgroup G4 along the optical axis toward the object side and moving thesecond lens group G2 and the aperture stop S along the optical axis suchthat a distance between the first lens group G1 and the second lensgroup G2 is increased, a distance between the second lens group G2 andthe third lens group G3 is decreased, and a distance between the thirdlens group G3 and the fourth lens group G4 is varied.

In the variable magnification optical system according to the presentexample, the third group G3 as a whole is moved along the optical axistoward the image side, thereby conducting focusing from an infinitelydistant object to a close distant object.

In the variable magnification optical system according to the presentexample, only the second segment lens group G42 in the fourth lens groupG4 is moved, as a vibration reduction lens group, to have a component ina direction perpendicular to the optical axis, thereby conductingvibration reduction.

In the variable magnification optical system according to the presentexample, in the wide-angle end state, the vibration reductioncoefficient is −0.92, and the focal length is 10.30 (mm), so that themoving amount of the second segment lens group G42 for correcting arotational camera shake of 0.62 degrees is −0.12 (mm). In the telephotoend state, the vibration reduction coefficient is −1.68, and the focallength is 97.00 (mm), so that the moving amount of the second segmentlens group G42 for correcting a rotational camera shake of 0.20 degreesis −0.20 (mm).

Table 3 below shows various values of the variable magnification of thepresent example.

TABLE 3 Third Example [Surface Data] m r d nd νd OP ∞  1 145.183 1.7002.00100 29.14  2 36.639 8.100 1.49782 82.57  3 −399.352 0.100 1.00000  443.208 6.000 1.88300 40.66  5 ∞  d5 1.00000 *6 436.597 0.100 1.5538938.09  7 87.003 1.100 1.83481 42.73  8 8.300 5.350 1.00000  9 −12.6071.000 1.75500 52.34 10 −32.799 0.800 1.00000 11 41.120 2.950 1.8080922.74 12 −19.604 0.900 1.88300 40.66 13 −73.132 d13 1.00000 14 ∞ d141.00000 Aperture Stop S 15 22.373 0.900 1.90265 35.73 16 12.230 3.4501.67003 47.14 17 −59.699 d17 1.00000 18 13.739 3.600 1.49782 82.57 19−24.820 0.900 2.00069 25.46 20 −270.014 2.200 1.00000 21 −117.055 2.0501.84666 23.80 22 −15.985 1.000 1.77377 47.25 *23  24.175 2.084 1.0000024 66.365 2.800 1.56883 56.00 25 −15.447 0.100 1.00000 26 44.994 2.7501.51742 52.20 27 −15.201 0.900 1.90366 31.27 28 29.993 0.300 1.00000 2914.609 5.050 1.67270 32.19 30 −9.200 0.900 2.00069 25.46 31 −24.3891.400 1.00000 32 −12.862 1.000 1.85135 40.10 *33  −27.495 BF 1.00000 I ∞[Aspherical Surface Data] m κ A4 A6 A8 A10 6 20.00000  9.17E−05−6.52E−07 2.70E−09 −1.24E−11 23 0.48230 −7.25E−06 −3.60E−07 4.06E−09 33−20.00000 −1.23E−04  8.28E−07 −6.05E−09  −9.89E−11 [Various Data] zoomratio 9.42 W M T f 10.30 30.00 96.99 FNO 4.12 5.48 5.80 2ω 80.89 29.729.45 Y 8.19 8.19 8.19 TL 103.03 121.38 143.32 [Upon focusing aninfinitely distant object] W M T f 10.30 30.00 96.99 d5 2.106 20.13140.209 d13 19.664 6.244 1.800 d14 4.279 4.974 1.800 d17 3.438 2.7435.916 BF 14.06 27.81 34.12 [Upon focusing on a closely distant object] WM T β −0.032 −0.068 −0.116 d5 2.106 20.131 40.209 d13 19.664 6.244 1.800d14 4.983 5.899 5.217 d17 2.733 1.818 2.499 BF 14.06 27.81 34.12 [LensGroup Data] ST f G1 1 64.10 G2 6 −10.17 G3 15 31.06 G4(R) 18 67.06[Values for Conditional Expression] (1) f1/f3 = 2.06 (2) f1/(−f2) = 6.30(3) (−fVR)/f3 = 0.92 (4) (−f2)/f3 = 0.33 (5) f3/fR = 0.46 (6) nd1 =2.00100

FIGS. 8A, 8B and 8C are graphs showing various aberrations of thevariable magnification optical system according to the third example ofthe present application upon focusing on an infinitely distant object,in which FIG. 8A is in a wide-angle end state, FIG. 8B is in anintermediate focal length state, and FIG. 8C is in a telephoto endstate.

FIGS. 9A and 9B are graphs showing meridional transverse aberration ofthe variable magnification optical system according to the third exampleupon focusing on an infinitely distant object in the wide-angle endstate with carrying out vibration reduction in which FIG. 9A is for arotational camera shake of 0.62 degrees in the wide-angle end state, andFIG. 9B is for a rotational camera shake of 0.20 degrees in a telephotoend state.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state, and also showssuperb optical performance upon carrying out vibration reduction.

According to the first to third examples, a variable magnificationoptical system that has high zoom ratio, is downsized and excellentoptical performance can be realized. In particular, the variablemagnification optical systems according to the first to third exampleseach has vibration reducing function and zoom ratio of about 10 and iscompact in size and light in weight, and angle of view in the wide-angleend state is more than 70 degrees, and variation in various aberrationsupon focusing on a closely distant object can be corrected excellently.

Hereinafter, a variable magnification optical system relating tonumerical examples according to the fourth embodiment of the presentapplication will be explained with reference to the accompanyingdrawings. Meanwhile, the fourth to the eighth examples are of the fourthembodiment.

Fourth Example

FIGS. 10A, 10B and 10C are sectional views showing a variablemagnification optical system according to a fourth example of the fourthembodiment of the present application, in which FIG. 10A shows sectionalview in a wide-angle end state, FIG. 10B shows sectional view in anintermediate focal length state, and FIG. 10C shows sectional view in atelephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a fourth lens group GR having positive refractivepower.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a positive meniscus lens L13 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 having a convex surface facing the objectside, a double concave negative lens L22, a double convex positive lensL23 and a negative meniscus lens L24 having a concave surface facing theobject side. The most object side negative meniscus lens L21 is a glassmold type aspherical lens whose object side lens surface is asphericallyshaped.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32. An aperture stop S is disposed at the object side ofthe third lens group G3.

The fourth lens group G4 consists of, in order from the object side, afront group G4F having negative refractive power and a rear group G4Rhaving positive refractive power.

The front group G4F consists of, in order from the object side, acemented lens constructed by a double convex positive lens L401 cementedwith a double concave negative lens L402 and a cemented lens constructedby a double concave negative lens L403 cemented with a positive meniscuslens L404 having a convex surface facing the object side. The negativelens L403 is a glass mold type aspherical lens whose object side lenssurface is aspherically shaped.

The rear group G4R consists of, in order from the object side, a doubleconvex positive lens L405, a cemented lens constructed by a doubleconvex positive lens L406 cemented with a negative meniscus lens L407having a concave surface facing the object side, a cemented lensconstructed by a negative meniscus lens L408 having a convex surfacefacing the object side cemented with a double convex positive lens L409,and a negative meniscus lens L410 having a convex surface having theimage side. The negative meniscus lens L410 is a glass mold typeaspherical lens whose image side lens surface is aspherically shaped.

Incidentally, in the variable magnification optical system according tothe present example, a low pass filter as well as a glass cover for asensor can be disposed between the fourth lens group G4 and the imageplane.

In the variable magnification optical system according to the presentexample, zooming from the wide-angle end state to the telephoto endstate, is conducted by moving the first lens group G1 to the fourth lensgroup G4 along the optical axis and moving the aperture stop S in a bodywith the front group G4F in the fourth lens group G4 such that adistance between the first lens group G1 and the second lens group G2 isincreased, a distance between the second lens group G2 and the thirdlens group G3 is decreased, a distance between the third lens group G3and the fourth lens group G4 is increased, and a distance between theaperture stop S and the third lens group G3 is decreased. In moredetail, upon zooming, the first lens group G1 and the third lens groupG3 are moved toward the object side. The second lens group G2 is movedtoward the object side from the wide-angle end state to the intermediatefocal length state and toward the image side from the intermediate focallength state to the telephoto end state. In the fourth lens group G4,upon zooming from the wide-angle end state to the telephoto end state,the front group G4F and the rear group G4R are moved toward the objectside from the wide-angle end state to the intermediate focal lengthstate and toward the image side from the intermediate focal length stateto the telephoto end state, such that a distance between the front groupG4F and the rear group G4R is decreased.

Table 4 below shows various values of the variable magnification opticalsystem according to the present example.

In table 4, f denotes a focal length, and BF denotes a back focal length(a distance on the optical axis between the most image side lens surfaceand the image plane I).

In [Surface Data], m denotes an order of an optical surface counted fromthe object side, r denotes a radius of curvature, d denotes asurface-to-surface distance (an interval from an n-th surface to an(n+1)-th surface, where n is an integer.), nd denotes refractive indexfor d-line (wavelength λ=587.6 nm) and νd denotes an Abbe number ford-line (wavelength λ=587.6 nm). Further, OP denotes an object surface,and I denotes an image plane. Meanwhile, radius of curvature r=∞ denotesa plane surface. The position of an aspherical surface is expressed byattaching “*” to the surface number, and in the column of the radius ofcurvature, a paraxial radius of curvature is shown.

In [Aspherical Data], with respect to an aspherical surface shown in[Surface Data], an aspherical surface coefficient and a conicalcoefficient are shown in the case where the aspherical surface isexhibited by the following expression:X=(h ² /r)/[1+[1−κ(h ² /r ²)]^(1/2) ]+A4h ⁴ +A6h ⁶ +A8h ⁸ +A10h ¹⁰where h denotes a vertical height from the optical axis, X denotes a sagamount which is a distance along the optical axis from the tangentsurface at the vertex of the aspherical surface to the asphericalsurface at the vertical height from the optical axis, x denotes aconical coefficient, A4, A6, A8 and A10 denote respective asphericalcoefficients, and r denotes a paraxial radius of curvature that is aradius of curvature of a reference sphere. “E−n”, where n is an integer,denotes “×10^(−n)”, for example, “1.234E−05” denotes “1.234×10⁻⁵”.The 2nd order aspherical surface coefficient A2 is 0, and omitted in thedescription.

In [Various Data], FNO denotes an f-number, c denotes a half angle ofview (unit “·”, Y denotes an image height, TL denotes a total length ofthe variable magnification optical system, that is, a distance along theoptical axis from the first surface to the image plane I upon focusingon an infinitely distant object, dn denotes a variable interval betweenan n-th surface and an (n+1)-th surface. φ denotes a diameter f theaperture stop S. Meanwhile, W denotes a wide-angle end state, M denotesan intermediate focal length state, and T denotes a telephoto end state.

In [Lens Group Data], a starting surface ST and a focal length of eachlens group are shown.

In [Values for Conditional Expressions], values corresponding torespective conditional expressions are shown.

It is noted, here, that “mm” is generally used for the unit of lengthsuch as the focal length f, the radius of curvature r and the unit forother lengths shown in Table 4. However, since similar opticalperformance can be obtained by an optical system proportionally enlargedor reduced its dimension, the unit is not necessarily to be limited to“mm”.

The explanation of reference symbols in Table 4 described above, is thesame in Tables for the fifth to eighth examples.

TABLE 4 Fourth Example [Surface Data] m r d nd νd OP ∞  1 104.51181.6000 2.003300 28.27  2 39.3751 7.4000 1.497820 82.57  3 −463.57010.1000  4 40.3116 5.4000 1.834810 42.73  5 241.9089  d5 *6 79.97111.0000 1.851350 40.10  7 8.1252 4.8500  8 −14.2116 1.0000 1.883000 40.66 9 124.9279 0.1000 10 30.8124 3.3500 1.808090 22.74 11 −15.1873 0.300012 −13.2222 1.0000 1.883000 40.66 13 −23.0302 d13 14 ∞ d14 Aperture StopS 15 26.1923 1.0000 1.954000 33.46 16 12.2483 2.8500 1.719990 50.27 17−43.5073 d17 18 14.5527 2.8500 1.497820 82.57 19 −40.3302 1.00001.950000 29.37 20 173.4596 2.1500 *21  −105.0156 1.0000 1.806100 40.7122 10.9037 2.2000 1.808090 22.74 23 28.6084 d23 24 30.6882 2.85001.579570 53.74 25 −18.3905 0.1000 26 18.8919 3.6000 1.518230 58.82 27−13.1344 1.0000 2.000690 25.46 28 −2198.5412 0.7500 29 412.2295 1.00001.954000 33.46 30 12.8823 3.5000 1.755200 27.57 31 −23.7185 1.1500 32−16.1296 1.0000 1.806100 40.71 *33  −97.3104 BF I ∞ [Aspherical SurfaceData] m 6 κ −8.7294 A4  4.64796E−05 A6 −4.09659E−07 A8  2.44519E−09 A10−9.90503E−12 m 21 κ −1.5760 A4  1.72590E−05 A6  9.45415E−08 A8−1.00397E−09 A10  0.00000E+00 m 33 κ −19.8082 A4 −1.67719E−05 A6−2.11776E−07 A8 −4.15932E−10 A10 −1.15008E−11 [Various Data] zoom ratio9.42 W T f 10.30 ~ 97.00 FNO 4.09 ~ 5.81 ω 40.21 ~ 4.76° Y 8.19 ~ 8.19 WM T f 10.30000 50.00013 97.00039 ω 40.21337 9.15519 4.75685 FNO 4.095.78 5.81 φ 7.68 8.50 9.20 TL 100.29944 130.25093 139.59967 d5 2.1000028.50000 39.66696 d13 17.38897 3.31447 2.00000 d14 4.87082 3.982621.60000 d17 2.59389 3.48209 5.86471 d23 5.29632 3.42829 3.30000 BF13.94944 33.44346 33.06800 [Lens Group Data] ST f G1 1 64.38705 G2 6−9.57903 G3 15 29.91408 G4 18 58.41425(W), 61.26584(M), 61.47193(T) G4F18 −81.48313 G4R 24 28.77173 [Values for Conditional Expression]  (7)ndh = 1.954(L31), 1.950(L402), 1.954(L408)  (8) νdh = 33.46(L31),29.37(L402), 33.46(L408)  (9) f1/(−f2) = 6.72 (10) (−f2)/f3 = 0.320 (12)νdh4 = 33.46(L408) (13) νdp1 = 82.57(L12) (14) νdp4 = 82.57(L401)

FIGS. 11A, 11B and 11C are graphs showing various aberrations of thevariable magnification optical system according to the first example ofthe present application upon focusing on an infinitely distant object,in which FIG. 11A is in a wide-angle end state, FIG. 11B is in anintermediate focal length state, and FIG. 11C is in a telephoto endstate.

In respective graphs, FNO denotes an f-number, A denotes an incidentangle of light rays, that is, a half angle of view (unit “·”). d denotesan aberration curve at d-line (wavelength λ=587.6 nm), and g denotes anaberration curve at g-line (wavelength λ=435.8 nm). Curves with no d norg denote aberrations at d-line. In the graph showing astigmatism, asolid line indicates a sagittal image plane, and a broken line indicatesa meridional image plane. Incidentally, the signs regarding variousaberration graphs of the present example are the same as the otherExamples of the fifth to eighth examples described hereinafter.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state.

Fifth Example

FIGS. 12A, 12B and 12C are sectional views showing a variablemagnification optical system according to a fifth example of the fourthembodiment of the present application, in which FIG. 12A shows sectionalview in a wide-angle end state, FIG. 12B shows sectional view in anintermediate focal length state, and FIG. 12C shows sectional view in atelephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a fourth lens group G4.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a positive meniscus lens L13 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, adouble concave negative lens L21, a double concave negative lens L22, adouble convex positive lens L23 and a negative meniscus lens L24 havinga concave surface facing the object side.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32. An aperture stop S is disposed at the object side ofthe third lens group G3.

The fourth lens group G4 consists of, in order from the object side, afront group G4F having negative refractive power and a rear group G4Rhaving positive refractive power.

The front group G4F consists of, in order from the object side, acemented lens constructed by a double convex positive lens L401 cementedwith a double concave negative lens L402 and a cemented lens constructedby a double concave negative lens L403 cemented with a positive meniscuslens L404 having a convex surface facing the object side. The negativelens L403 is a glass mold type aspherical lens whose object side lenssurface is aspherically shaped.

The rear group G4R consists of, in order from the object side, a doubleconvex positive lens L405 and a cemented lens constructed by a positivemeniscus lens L406 having a concave surface facing the object sidecemented with a negative meniscus lens L407 having a concave surfacefacing the object side. The positive lens L405 is a glass mold typeaspherical lens whose object side lens surface is aspherically shaped.

Incidentally, in the variable magnification optical system according tothe present example, a low pass filter as well as a glass cover for asensor can be disposed between the fourth lens group G4 and the imageplane.

In the variable magnification optical system according to the presentexample, zooming from the wide-angle end state to the telephoto endstate, is conducted by moving the first lens group G1 to the fourth lensgroup G4 along the optical axis and moving the aperture stop S in a bodywith the front group G4F in the fourth lens group G4 such that adistance between the first lens group G1 and the second lens group G2 isincreased, a distance between the second lens group G2 and the thirdlens group G3 is decreased, a distance between the third lens group G3and the fourth lens group G4 is increased, and a distance between theaperture stop S and the third lens group G3 is decreased. In moredetail, upon zooming, the first lens group G1 and the third lens groupG3 are moved toward the object side. The second lens group G2 is movedtoward the object side from the wide-angle end state to the intermediatefocal length state and toward the image side from the intermediate focallength state to the telephoto end state. In the fourth lens group G4,upon zooming from the wide-angle end state to the telephoto end state,the front group G4F and the rear group G4R are moved toward the objectside such that a distance between the front group G4F and the rear groupG4R is decreased.

Table 5 below shows various values of the variable magnification of thepresent example.

TABLE 5 Fifth Example [Surface Data] m r d nd νd OP ∞  1 251.8446 1.60001.950000 29.37  2 36.8495 7.9000 1.497820 82.57  3 −162.8867 0.1000  441.6898 5.7500 1.883000 40.66  5 7827.2710  d5  6 −808.8261 1.00001.883000 40.66  7 9.5148 3.6000  8 −15.5435 1.0000 1.883000 40.66  9143.0303 0.1000 10 28.6318 3.0500 1.808090 22.74 11 −13.3111 0.2500 12−12.1771 1.0000 1.834810 42.73 13 −36.4394 d13 14 ∞ d14 Aperture Stop S15 27.0772 1.0000 2.000690 25.46 16 15.7705 2.5000 1.744000 44.80 17−35.2142 d17 18 12.6941 2.9500 1.497820 82.57 19 −24.8876 1.00001.846660 23.80 20 775.1758 2.1500 *21  −227.6550 1.0000 1.806100 40.9722 8.8217 2.2000 1.846660 23.80 23 19.5840 d23 *24  15.0000 3.15001.583130 59.42 25 −23.9888 0.1000 26 −509.6518 4.2000 1.581440 40.98 27−7.8594 1.0000 1.954000 33.46 28 −200.0000 BF I ∞ [Aspherical SurfaceData] M 21 κ −20.0000 A4  1.61374E−05 A6 −2.79859E−08 A8 −1.22068E−09A10  0.00000E+00 M 24 κ 3.6281 A4 −1.21377E−04 A6 −7.10924E−07 A8 1.36403E−08 A10 −4.10781E−10 [Various Data] zoom ratio 9.42 W T f 10.30~ 97.00 FNO 4.12 ~ 6.48 ω 43.07 ~ 4.70° Y 8.19 ~ 8.19 W M T f 10.3000050.00001 96.99995 ω 43.07103 9.11914 4.70123 FNO 4.12 5.81 6.48 φ 6.807.90 7.90 TL 90.80323 122.13334 131.09941 d5 2.28937 28.97477 38.62002d13 13.12572 3.71901 2.00000 d14 6.29895 3.32684 1.40000 d17 2.433675.40578 7.33262 d23 6.60623 3.30000 3.30000 BF 13.44928 30.8069331.84677 [Lens Group Data] ST f G1 1 59.94630 G2 6 −8.99248 G3 1524.34092 G4 18 71.07089(W), 75.48860(M), 75.48860(T) G4F 18 −112.21259G4R 24 35.78226 [Values for Conditional Expression]  (7) ndh =1.950(L11), 1.954(L407)  (8) νdh = 29.37(L11), 33.46(L407)  (9) f1/(−f2)= 6.67 (10) (−f2)/f3 = 0.369 (11) |fh/f1| = 0.761(L11) (12) νdh4 =33.46(L407) (13) νdp1 = 82.57(L12) (14) νdp4 = 82.57(L401)

FIGS. 13A, 13B and 13C are sectional views showing a variablemagnification optical system according to a fifth example of the presentapplication, in which FIG. 13A shows sectional view in a wide-angle endstate, FIG. 13B shows sectional view in an intermediate focal lengthstate, and FIG. 13C shows sectional view in a telephoto end state.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state.

Sixth Example

FIGS. 14A, 14B and 14C are sectional views showing a variablemagnification optical system according to a sixth example of the fourthembodiment of the present application, in which FIG. 14A shows sectionalview in a wide-angle end state, FIG. 14B shows sectional view in anintermediate focal length state, and FIG. 14C shows sectional view in atelephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a fourth lens group G4 having positive refractivepower.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a positive meniscus lens L13 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 having a convex surface facing the objectside, a double concave negative lens L22, a double convex positive lensL23 and a negative meniscus lens L24 having a concave surface facing theobject side. The negative meniscus lens L21 is a glass mold typeaspherical lens whose object side lens surface is aspherically shaped.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32. An aperture stop S is disposed at the object side ofthe third lens group G3.

The fourth lens group G4 consists of, in order from the object side, afront group G4F having negative refractive power and a rear group G4Rhaving positive refractive power.

The front group G4F consists of, in order from the object side, acemented lens constructed by a double convex positive lens L401 cementedwith a negative meniscus lens L402 having a convex surface facing theimage side and a cemented lens constructed by a double concave negativelens L403 cemented with a positive meniscus lens L404 having a convexsurface facing the object side. The negative lens L403 is a glass moldtype aspherical lens whose object side lens surface is asphericallyshaped.

The rear group G4R consists of, in order from the object side, a doubleconvex positive lens L405 and a cemented lens constructed by a doubleconvex positive lens L406 cemented with a negative meniscus lens L407having a concave surface facing the object side. The positive lens L405is a glass mold type aspherical lens whose object side lens surface isaspherically shaped.

Incidentally, in the variable magnification optical system according tothe present example, a low pass filter as well as a glass cover for asensor can be disposed between the fourth lens group G4 and the imageplane.

In the variable magnification optical system according to the presentexample, zooming from the wide-angle end state to the telephoto endstate, is conducted by moving the first lens group G1 to the fourth lensgroup G4 along the optical axis and moving the aperture stop S in a bodywith the front group G4F in the fourth lens group G4 such that adistance between the first lens group G1 and the second lens group G2 isincreased, a distance between the second lens group G2 and the thirdlens group G3 is decreased, a distance between the third lens group G3and the fourth lens group G4 is increased, and a distance between theaperture stop S and the third lens group G3 is decreased. In moredetail, upon zooming, the first lens group G1 and the third lens groupG3 are moved toward the object side. The second lens group G2 is movedtoward the object side from the wide-angle end state to the intermediatefocal length state and toward the image side from the intermediate focallength state to the telephoto end state. In the fourth lens group G4,upon zooming from the wide-angle end state to the telephoto end state,the front group G4F and the rear group G4R are moved toward the objectside such that a distance between the front group G4F and the rear groupG4R is decreased.

Table 6 below shows various values of the variable magnification of thepresent example.

TABLE 6 Sixth Example [Surface Data] m r d nd νd OP ∞  1 149.8692 1.60001.949665 27.56  2 44.3736 6.8398 1.497820 82.51  3 −243.5058 0.1000  445.3756 5.3508 1.867900 41.78  5 311.4136  d5 *6 89.0243 1.2000 1.83481042.73  7 8.4900 3.7581  8 −15.7255 1.0000 1.834810 42.73  9 250.00000.1000 10 25.2749 3.2925 1.808090 22.74 11 −17.4750 0.5480 12 −12.61961.0000 1.816000 46.59 13 −33.4252 d13 14 ∞ d14 Aperture Stop S 1529.1681 1.0000 1.889044 39.77 16 18.2404 3.2071 1.593125 66.16 17−26.5261 d17 18 14.2857 3.5654 1.497820 82.51 19 −21.9776 1.00001.902000 25.23 20 −82.8398 2.2052 *21  −52.3071 1.0000 1.848976 43.01 229.1414 2.6915 1.950000 29.37 23 25.8642 d23 *24  35.4414 3.3350 1.58913061.22 25 −21.3191 0.3000 26 42.3100 4.4029 1.581440 40.98 27 −10.19791.2000 1.954000 33.46 28 −300.4717 BF I ∞ [Aspherical Surface Data] m 6κ 1.0000 A4 3.45801E−05 A6 −1.38520E−07  A8 −5.59965E−11  A101.26030E−11 m 21 κ 1.0000 A4 1.74477E−06 A6 1.28096E−07 A8 −2.63692E−09 A10 0.00000E+00 m 24 κ 1.0000 A4 −1.22983E−05  A6 1.47314E−07 A8−5.48742E−10  A10 0.00000E+00 [Various Data] zoom ratio 9.42 W T f 10.30~ 97.00 FNO 3.50 ~ 5.62 ω 39.90 ~ 4.69° Y 8.19 ~ 8.19 W M T f 10.3000149.99971 96.99932 ω 39.90076 9.01930 4.68610 FNO 3.50 5.20 5.62 φ 8.998.81 9.00 TL 99.25773 129.21001 139.67596 d5 1.99991 30.68218 41.26022d13 18.53440 4.14191 2.00000 d14 3.76478 2.96318 1.40000 d17 3.541814.34341 5.90655 d23 8.01786 3.30678 3.30001 BF 14.70262 35.0762137.11281 [Lens Group Data] ST f G1 1 66.85483 G2 6 −9.36043 G3 1527.88295 G4 18 53.04244(W), 55.61603(M), 55.61991(T) G4F 18 −160.91663G4R 24 33.55859 [Values for Conditional Expression]  (7) ndh =1.950(L404), 1.954(L407)  (8) νdh = 29.37(L404), 33.46(L407)  (9)f1/(−f2) = 7.14 (10) (−f2)/f3 = 0.336 (12) νdh4 = 33.46(L407) (13) νdp1= 82.51(L12) (14) νdp4 = 82.51(L401)

FIGS. 15A, 15B and 15C are graphs showing various aberrations of thevariable magnification optical system according to the sixth example ofthe present application upon focusing on an infinitely distant object,in which FIG. 15A is in a wide-angle end state, FIG. 15B is in anintermediate focal length state, and FIG. 15C is in a telephoto endstate.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state.

Seventh Example

FIGS. 16A, 16B and 16C are sectional views showing a variablemagnification optical system according to a seventh example of thefourth embodiment of the present application, in which FIG. 16A showssectional view in a wide-angle end state, FIG. 16B shows sectional viewin an intermediate focal length state, and FIG. 16C shows sectional viewin a telephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a fourth lens group G4 having positive refractivepower.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a positive meniscus lens L13 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 having a convex surface facing the objectside, a negative meniscus lens L22 having a concave surface facing theobject side, a double convex positive lens L23 and a negative meniscuslens L24 having a concave surface facing the object side. Meanwhile, thenegative meniscus lens L21 is a glass mold type aspherical lens whoseobject side lens surface is aspherically shaped.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32. Meanwhile, an aperture stop S is disposed at theobject side of the third lens group G3.

The fourth lens group G4 consists of, in order from the object side, acemented lens constructed by a double convex positive lens L401 cementedwith a negative meniscus lens L402 having a convex surface facing theimage side, a cemented lens constructed by a positive meniscus lens L403having a concave surface facing the object side cemented with a doubleconcave negative lens L404, a double convex positive lens L405, acemented lens constructed by a positive meniscus lens L406 having aconcave surface facing the object side cemented with a double concavenegative lens L407, a cemented lens constructed by a negative meniscuslens L408 having a convex surface facing the object side cemented with adouble convex positive lens L409, and a negative meniscus lens L410having a concave surface facing the object side. Meanwhile, the positivemeniscus lens L403 is a glass mold type aspherical lens whose objectside lens surface is aspherically shaped, and the negative meniscus lensL410 is a glass mold type aspherical lens whose image side lens surfaceis aspherically shaped.

Incidentally, in the variable magnification optical system according tothe present example, a low pass filter as well as a glass cover for asensor can be disposed between the fourth lens group G4 and the imageplane.

In the variable magnification optical system according to the presentexample, zooming from the wide-angle end state to the telephoto endstate, is conducted by moving the first lens group G1 to the fourth lensgroup G4 along the optical axis and moving the aperture stop S in a bodywith the fourth lens group G4 such that a distance between the firstlens group G1 and the second lens group G2 is increased, a distancebetween the second lens group G2 and the third lens group G3 isdecreased, a distance between the third lens group G3 and the fourthlens group G4 is increased, and a distance between the aperture stop Sand the third lens group G3 is decreased. In more detail, upon zooming,the first lens group G1, the third lens group G3 and the fourth lensgroup G4 are moved toward the object side. The second lens group G2 ismoved toward the object side from the wide-angle end state to theintermediate focal length state and toward the image side from theintermediate focal length state to the telephoto end state.

Table 7 below shows various values of the variable magnification of thepresent example.

TABLE 7 Seventh Example [Surface Data] m r d nd νd OP ∞  1 134.94161.6000 2.001000 29.14  2 37.4620 7.6500 1.497820 82.57  3 −339.56740.1000  4 41.6639 5.5500 1.883000 40.66  5 520.6025  d5 *6 2429.76491.0000 1.851350 40.10  7 8.6673 5.7500  8 −10.8429 1.0000 1.487490 70.31 9 −45.5363 0.8500 10 52.5147 3.1000 1.808090 22.74 11 −17.4657 0.300012 −16.1357 1.0000 1.954000 33.46 13 −39.2793 d13 14 ∞ d14 Aperture StopS 15 29.3843 1.0000 1.902650 35.73 16 14.8567 2.8000 1.719990 50.27 17−55.5590 d17 18 13.5564 3.3500 1.497820 82.57 19 −24.9755 1.00001.950000 29.37 20 −183.0794 2.1500 *21  −145.2052 2.2500 1.802440 25.5522 −14.7800 1.0000 1.766840 46.78 23 23.7425 2.8000 24 25.8106 3.00001.516800 63.88 25 −15.0644 0.1000 26 −568.8377 3.0000 1.568830 56.00 27−9.3137 1.0000 1.954000 33.46 28 98.3635 0.1000 29 15.0059 1.00001.950000 29.37 30 7.0809 4.2500 1.647690 33.73 31 −21.2496 1.4500 32−11.4669 1.0000 1.743300 49.32 *33  −29.8012 BF I ∞ [Aspherical SurfaceData] m  6 κ −20.0000 A4  9.19258E−05 A6 −6.71049E−07 A8  3.76181E−09A10 −1.11659E−11 m 21 κ −13.2727 A4  1.25451E−05 A6  1.56196E−07 A8−2.20815E−09 A10  0.00000E+00 m 33 κ    −0.9208 A4 −8.91367E−05 A6−1.72158E−06 A8  2.40673E−08 A10 −6.77013E−10 [Various Data] Zoom ratio9.42 W T f 10.30 ~ 97.00 FNO 4.08 ~ 5.83 ω 40.21 ~ 4.78° Y 8.19 ~ 8.19 WM T f 10.30000 50.00021 97.00042 ω 40.21108 9.16962 4.78008 FNO 4.085.79 5.83 φ 8.40 9.20 10.10 TL 102.69006 133.09448 142.59913 d5 2.1000029.30442 39.87067 d13 19.87565 4.17251 2.00000 d14 4.49060 3.806721.60000 d17 3.02442 3.70831 5.91502 BF 14.04941 32.95254 34.06346 [LensGroup Data] ST f G1 1 63.95755 G2 6 −10.21809 G3 15 32.27954 G4 1870.96006 [Values for Conditional Expression]  (7) ndh = 2.001(L11),1.954(L24), 1.950(L402), 1.954(L407), 1.950(L408)  (8) νdh = 29.14(L11),33.46(L24), 29.37(L402), 33.46(L407), 29.37(L408)  (9) f1/(−f2) = 6.26(10) (−f2)/f3 = 0.317 (11) |fh/f1| = 0.817(L11) (12) νdh4 = 33.46(L407)(13) νdp1 = 82.57(L12) (14) νdp4 = 82.57(L401)

FIGS. 17A, 17B and 17C are graphs showing various aberrations of thevariable magnification optical system according to the seventh exampleof the present application upon focusing on an infinitely distantobject, in which FIG. 17A is in a wide-angle end state, FIG. 17B is inan intermediate focal length state, and FIG. 17C is in a telephoto endstate.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state.

Eighth Example

FIGS. 18A, 18B and 18C are sectional views showing a variablemagnification optical system according to an eighth example of thefourth embodiment of the present application, in which FIG. 18A showssectional view in a wide-angle end state, FIG. 18B shows sectional viewin an intermediate focal length state, and FIG. 18C shows sectional viewin a telephoto end state.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; and a fourth lens group G4 having positive refractivepower.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 having aconvex surface facing the object side cemented with a double convexpositive lens L12, and a plano-convex lens L13 having a convex surfacefacing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 having a convex surface facing the objectside, a negative meniscus lens L22 having a concave surface facing theobject side, a cemented lens constructed by a double convex positivelens L23 cemented with a negative meniscus lens L24 having a concavesurface facing the object side. Meanwhile, the negative meniscus lensL21 is a compound type aspherical lens whose object side glass surfaceis provided with a resin layer.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L31 having aconvex surface facing the object side cemented with a double convexpositive lens L32.

The fourth lens group G4 consists of, in order from the object side, acemented lens constructed by a double convex positive lens L401 cementedwith a negative meniscus lens L402 having a convex surface facing theimage side, a cemented lens constructed by a positive meniscus lens L403having a concave surface facing the object side cemented with a doubleconcave negative lens L404, a double convex positive lens L405, acemented lens constructed by a double convex positive lens L406 cementedwith a double concave negative lens L407, a cemented lens constructed bya double convex positive lens L408 cemented with a negative meniscuslens L409 having a convex surface facing the image side, and a negativemeniscus lens L410 having a concave surface facing the object side.Meanwhile, the negative meniscus lens L404 is a glass mold typeaspherical lens whose image side lens surface is aspherically shaped,and the negative meniscus lens L410 is a glass mold type aspherical lenswhose image side lens surface is aspherically shaped.

Incidentally, in the variable magnification optical system according tothe present example, a low pass filter as well as a glass cover for asensor can be disposed between the fourth lens group G4 and the imageplane I.

In the variable magnification optical system according to the presentexample, zooming from the wide-angle end state to the telephoto endstate, is conducted by moving the first lens group G1 to the fourth lensgroup G4 along the optical axis toward the object side and moving theaperture stop S in a body with the fourth lens group G4 such that adistance between the first lens group G1 and the second lens group G2 isincreased, a distance between the second lens group G2 and the thirdlens group G3 is decreased, a distance between the third lens group G3and the fourth lens group G4 is increased from the wide-angle end stateto the intermediate focal length state and is decreased from theintermediate focal length state to the telephoto end state, and adistance between the aperture stop S and the third lens group G3 isincreased from the wide-angle end state to the intermediate focal lengthstate and is decreased from the intermediate focal length state to thetelephoto end state.

Table 8 below shows various values of the variable magnification of thepresent example.

TABLE 8 Eighth Example [Surface Data] m r d nd νd OP ∞  1 145.18311.7000 2.001000 29.14  2 36.6390 8.1000 1.497820 82.57  3 −399.35190.1000  4 43.2076 6.0000 1.883000 40.66  5 ∞  d5 *6 436.5967 0.10001.553890 38.09  7 87.0031 1.1000 1.834810 42.73  8 8.3001 5.3500  9−12.6073 1.0000 1.755000 52.34 10 −32.7993 0.8000 11 41.1197 2.95001.808090 22.74 12 −19.6043 0.9000 1.883000 40.66 13 −73.1316 d13 14 ∞d14 Aperture Stop S 15 22.3725 0.9000 1.902650 35.73 16 12.2299 3.45001.670030 47.14 17 −59.6992 d17 18 13.7390 3.6000 1.497820 82.57 19−24.8201 0.9000 2.000690 25.46 20 −270.0138 2.2000 21 −117.0547 2.05001.846660 23.80 22 −15.9850 1.0000 1.773770 47.25 *23  24.1750 2.0836 2466.3654 2.8000 1.568830 56.00 25 −15.4473 0.1000 26 44.9939 2.75001.517420 52.20 27 −15.2012 0.9000 1.903660 31.27 28 29.9926 0.3000 2914.6093 5.0500 1.672700 32.19 30 −9.1997 0.9000 2.000690 25.46 31−24.3892 1.4000 32 −12.8617 1.0000 1.851350 40.10 *33  −27.4946 BF I ∞[Aspherical Surface Data] m 6 κ 20.0000 A4  9.17458E−05 A6 −6.51986E−07A8  2.69890E−09 A10 −1.23751E−11 m 23 κ 0.4823 A4 −7.24815E−06 A6−3.60139E−07 A8  4.05630E−09 A10  0.00000E+00 m 33 κ −20.0000 A4−1.22780E−04 A6  8.28360E−07 A8 −6.05245E−09 A10 −9.88805E−11 [VariousData] zoom ratio 9.42 W T f 10.30 ~ 96.99 FNO 4.12 ~ 5.81 ω 40.44 ~4.73° Y 8.19 ~ 8.19 W M T f 10.30260 30.00000 96.99284 ω 40.4428314.85841 4.72723 FNO 4.12 5.48 5.81 φ 8.12 8.12 9.70 TL 103.02710121.37977 143.32397 d5 2.10606 20.13084 40.20889 d13 19.66416 6.243591.80000 d14 4.27874 4.97381 1.80000 d17 3.43763 2.74256 5.91637 BF14.05688 27.80535 34.11509 [Lens Group Data] ST f G1 1 64.09778 G2 6−10.16794 G3 15 31.06055 G4 18 67.05869 [Values for ConditionalExpression]  (7) ndh = 2.001(L11)  (8) νdh = 29.14(L11)  (9) f1/(−f2) =6.31 (10) (−f2)/f3 = 0.327 (11) |fh/f1| = 0.770(L11) (13) νdp1 =82.57(L12) (14) νdp4 = 82.57(L401)

FIGS. 19A, 19B and 19C are graphs showing various aberrations of thevariable magnification optical system according to the eighth example ofthe present application upon focusing on an infinitely distant object,in which FIG. 19A is in a wide-angle end state, FIG. 19B is in anintermediate focal length state, and FIG. 19C is in a telephoto endstate.

As is apparent from the respective graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance as a result of good corrections to various aberrations fromthe wide-angle end state to the telephoto end state.

According to the fourth to the eighth examples, a variable magnificationoptical system that is downsized and has high optical performance can berealized.

Incidentally, the above described examples each only shows a specificexample of the invention of the present application, and accordingly thepresent invention is not limited to them. The following description maysuitably be applied within limits that do not deteriorate opticalperformance of the variable magnification optical system according tothe first to the fourth embodiments of the present application.

As the numerical examples of the variable magnification optical systemaccording to the first to the fourth embodiments of the presentapplication, although zoom lenses having a four-lens-group configurationand a five-lens-group configuration have been shown, the presentapplication are not limited to them and can be applied to other lensconfigurations such as a six-lens-group configuration. Specifically, alens configuration in which a lens or a lens group is added to the mostobject side, or the most image side of the variable magnificationoptical system according to the first to the fourth embodiments of thepresent application is possible. Incidentally, a lens group is definedas a portion including at least one lens separated by air spaces.

In a variable magnification optical system according to the first to thefourth embodiments of the present application, in order to vary focusingfrom infinitely distant object to a close object, a portion of a lensgroup, a single lens group, or a plurality of lens groups may be movedalong the optical axis as a focusing lens group. It is particularlypreferable that at least a portion of the second lens group, a portionof the third lens group or a portion of the fourth lens group is movedas the focusing lens group. In this case, the focusing lens group can beused for auto focus, and suitable for being driven by a motor such as anultrasonic motor.

Moreover, in a variable magnification optical system according to thefirst to the fourth embodiments of the present application, a lens groupas a whole or a portion of a lens group may be moved as a vibrationreduction lens group to have a component in a direction perpendicular tothe optical axis, or tilted (swayed) in a direction including theoptical axis, thereby correcting an image blur caused by a camera shake.In particular, at least a portion of the third lens group or a portionof the fourth lens group is preferably made as the vibration reductionlens group.

In a variable magnification optical system according to the first to thefourth embodiments of the present application, any lens surface may be aspherical surface, a plane surface, or an aspherical surface. When alens surface is a spherical surface or a plane surface, lens processing,assembling and adjustment become easy, and deterioration in opticalperformance caused by lens processing, assembling and adjustment errorscan be prevented, so that it is preferable. Moreover, even if the imageplane is shifted, deterioration in optical performance is little, sothat it is preferable. When a lens surface is an aspherical surface, theaspherical surface may be fabricated by a fine grinding process, a glassmolding process that a glass material is formed into an aspherical shapeby a mold, or a compound type process that a resin material is formedinto an aspherical shape on a glass lens surface. A lens surface may bea diffractive optical surface, and a lens may be a graded-index typelens (GRIN lens) or a plastic lens.

In a variable magnification optical system according to the first to thefourth embodiments of the present application, although an aperture stopis preferably disposed in the third lens group or in the neighborhood ofthe third lens group, the function may be substituted by a lens framewithout disposing a member as an aperture stop.

Moreover, the lens surface of the lenses composing the variablemagnification optical system according to the first to the fourthembodiments of the present application may be applied with ananti-reflection coating having a high transmittance in a broadwavelength range. With this contrivance, it is feasible to attain thehigh contrast and the high optical performance by reducing a flare andghost images.

In a variable magnification optical system according to the first to thefourth embodiments of the present application, the zoom ratio is about 5to 20.

Next, a camera, which is an optical apparatus equipped with the variablemagnification optical system according to the first to the fourthembodiments of the present application, is explained with referring toFIG. 20 .

FIG. 20 is a view showing a configuration of a camera equipped with thevariable magnification optical system according to the first to thefourth embodiments of the present application.

In FIG. 20 , the camera 1 is a so-called mirror-less camera of a lensinterchangeable type equipped with the variable magnification opticalsystem according to the first to the fourth embodiments of the presentapplication as an imaging lens 2.

In the camera 1, light emitted from an unillustrated object is convergedby the imaging lens 2, through an OLPF (optical low pass filter), andforms an object image on an imaging surface of an imaging portion 3. Theobject image is photo-electrically converted by a photo-electricconversion element provided in the imaging portion 3 so that a pictureof the object is formed. This picture is displayed on an EVF (Electronicview finder) 4. Thus, a photographer can observe the object through theEVF 4.

When the photographer presses an unillustrated release button, thepicture of the object formed by the imaging portion 3 is stored in anunillustrated memory. In this manner, the photographer can take apicture of the object by the camera 1.

Here, the variable magnification optical system according to the firstexample installed in the camera 1 as the imaging lens 2 is a variablemagnification optical system that has an excellent optical performance.Accordingly, the camera 1 can realize excellent optical performance.Further, even if a variable magnification optical system according tothe second to the eighth examples is installed in a camera as an imaginglens 2, the same effect as that of the camera 1 can be attained.Further, even if a variable magnification optical system according toeach of the above described examples is installed in a single lensreflex camera of the type which is provided with a quick return mirrorand in which an object is observed through a finder optical system, thesame effect as that of the camera 1 can be attained.

Finally, an outline of a method for manufacturing a variablemagnification optical system according to the first to the fourthembodiments of the present application, is described with referring toFIG. 21 to FIG. 24 .

The method for manufacturing the variable magnification optical systemaccording to the first embodiment of the present application shown inFIG. 21 , is a method for manufacturing a variable magnification opticalsystem, comprising, in order from an object side: a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; an aperture stop; a third lens group having positiverefractive power; and a rear lens group; and the method comprises thefollowing steps of S11 to S14:

Step S11: disposing each lens group and the aperture stop, in order fromthe object side, in a lens barrel, and constructing, by providing aknown movement mechanism in the lens barrel, such that, upon zoomingfrom a wide angle end state to a telephoto end state, at least the rearlens group is moved toward the object side, and a distance between thefirst lens group and the second lens group, a distance between thesecond lens group and the third lens group and a distance between thethird lens group and the rear lens group are varied.

Step S12: providing a known movement mechanism in the lens barrel andconstructing such that, upon focusing on from an infinitely distantobject to a closely distant object, the third lens group as a whole ismoved in the direction of the optical axis. Step S13: providing a knownmovement mechanism and constructing at least a portion of the rear lensgroup to be moved to have a component in a direction perpendicular tothe optical axis, as a vibration reduction lens group.

Step S14: constructing such that the vibration reduction lens group hasnegative refractive power.

Thus, the method for manufacturing a variable magnification opticalsystem according to the first embodiment of the present applicationmakes it possible to manufacture a variable magnification optical systemthat has high zoom ratio, is downsized and has excellent opticalperformance.

The method for manufacturing the variable magnification optical systemaccording to the second embodiment of the present application shown inFIG. 22 , is a method for manufacturing a variable magnification opticalsystem, comprising, in order from an object side: a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; a third lens group having positive refractive power;and a rear lens group; and the method comprises the following steps ofS21 to S25:

Step S21: disposing respective lens groups, in order from the objectside, in a lens barrel, and constructing, by providing a known movementmechanism in the lens barrel, such that, upon zooming from a wide-angleend state to a telephoto end state, at least the first lens group andthe rear lens group are moved toward the object side, and that adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group and adistance between the third lens group and the rear lens group arevaried.

Step S22: providing a known movement mechanism in the lens barrel andconstructing such that, upon focusing on from an infinitely distantobject to a closely distant object, the third lens group as a whole ismoved in the direction of the optical axis. Step S23: providing a knownmovement mechanism and constructing at least a portion of the rear lensgroup to be moved to have a component in a direction perpendicular tothe optical axis, as a vibration reduction lens group.

Step S24: constructing such that the vibration reduction lens group hasnegative refractive power.

Step S25: constructing such that the third lens group and the vibrationreduction lens group satisfy the following conditional expression (3):0.20<(−fVR)/f3<1.20  (3)where fVR denotes a focal length of the vibration reduction lens group,and f3 denotes a focal length of the third lens group.

Thus, the method for manufacturing a variable magnification opticalsystem according to the second embodiment of the present applicationmakes it possible to manufacture a variable magnification optical systemthat has high zoom ratio, is downsized and has excellent opticalperformance.

The method for manufacturing the variable magnification optical systemaccording to the third embodiment of the present application shown inFIG. 23 , is a method for manufacturing a variable magnification opticalsystem, comprising, in order from an object side: a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; an aperture stop; a third lens group having positiverefractive power; and a rear lens group; and the method comprises thefollowing steps of S31 to S33:

Step S31: constructing such that the third lens group is composed of acemented lens constructed by a positive lens and a negative lens.

Step 32: disposing each lens group and the aperture stop, in order fromthe object side, in a lens barrel, and constructing, by providing aknown movement mechanism in the lens barrel, such that, upon zoomingfrom a wide-angle end state to a telephoto end state, at least the rearlens group is moved toward the object side, and a distance between thefirst lens group and the second lens group, a distance between thesecond lens group and the third lens group and a distance between thethird lens group and the rear lens group are varied.

Step 33: providing a known movement mechanism in the lens barrel andconstructing such that, upon focusing on from an infinitely distantobject to a closely distant object, the third lens group as a whole ismoved in the direction of the optical axis.

Thus, the method for manufacturing a variable magnification opticalsystem according to the third embodiment of the present applicationmakes it possible to manufacture a variable magnification optical systemthat has high zoom ratio, is downsized and has excellent opticalperformance.

The method for manufacturing the variable magnification optical systemaccording to the fourth embodiment of the present application shown inFIG. 24 , is a method for manufacturing a variable magnification opticalsystem, comprising, in order from an object side: a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; a third lens group having positive refractive power;and a fourth lens group having positive refractive power; and the methodcomprises the following steps of S41 to S42:

Step S41: disposing each lens group in a lens barrel in order from theobject side such that the variable magnification optical system has atleast one lens that satisfies the following conditional expressions (7)and (8):1.928<ndh  (7)28.60<νdh  (8)where ndh denotes refractive index at d-line (wavelength λ=587.6 nm) ofthe said lens, and νdh denotes Abbe number at d-line (wavelength λ=587.6nm) of the said lens.

Step S42: providing a known movement mechanism in the lens barrel andconstructing such that, upon focusing from an infinitely distant objectto a closely distant object, a distance between the first lens group andthe second lens group, a distance between the second lens group and thethird lens group, and a distance between the third lens group and thefourth lens group are varied.

Thus, the method for manufacturing a variable magnification opticalsystem according to the fourth embodiment of the present applicationmakes it possible to manufacture a variable magnification optical systemthat is downsized and has excellent optical performance.

What is claimed is:
 1. A variable magnification optical systemcomprising, in order from an object side: a first lens group havingpositive refractive power; a second lens group having negativerefractive power; a third lens group having positive refractive power;and a rear lens group; upon zooming, a distance between the first lensgroup and the second lens group, a distance between the second lensgroup and the third lens group, and a distance between the third lensgroup and the rear lens group being varied, and the second lens groupand the third lens group being moved; and the following conditionalexpression being satisfied:5.00<f1/(−f2)<10.00 where f1 denotes a focal length of the first lensgroup, and f2 denotes a focal length of the second lens group, whereinat least one lens satisfies the following conditional expressions:1.928<ndh28.60<νdh where ndh denotes refractive index at d-line (wavelengthλ=587.6 nm) of the lens, and νdh denotes Abbe number at d-line(wavelength λ=587.6 nm) of the lens.
 2. The variable magnificationoptical system according to claim 1, wherein the first lens group movestoward the object side upon zooming from a wide-angle end state to atelephoto end state.
 3. The variable magnification optical systemaccording to claim 1, wherein the rear lens group moves toward theobject side upon zooming from the wide-angle end state to the telephotoend state.
 4. The variable magnification optical system according toclaim 1, wherein at least a portion of the rear lens group is moved as avibration reduction lens group to have a movement component in adirection perpendicular to the optical axis, and the vibration reductionlens group has negative refractive power.
 5. The variable magnificationoptical system according to claim 1, wherein at least a portion of therear lens group is moved as a vibration reduction lens group to have amovement component in a direction perpendicular to the optical axis, andthe vibration reduction lens group comprises a cemented lens constructedby a positive lens cemented with a negative lens.
 6. The variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:0.42<f3/fR<0.80 where f3 denotes a focal length of the third lens group,and fR denotes a focal length of the rear lens group in a wide-angle endstate.
 7. The variable magnification optical system according to claim1, wherein an aperture stop is disposed between the second lens groupand the third lens group.
 8. A method for manufacturing a variablemagnification optical system, comprising: arranging, in order from anobject side: a first lens group having positive refractive power; asecond lens group having negative refractive power; a third lens grouphaving positive refractive power; and a rear lens group; constructingsuch that, upon zooming, a distance between the first lens group and thesecond lens group, a distance between the second lens group and thethird lens group, and a distance between the third lens group and therear lens group are varied, and the second lens group and the third lensgroup are moved; satisfying the following conditional expression:5.00<f1/(−f2)<10.00 where f1 denotes a focal length of the first lensgroup, and f2 denotes a focal length of the second lens group; and atleast one lens satisfying the following conditional expressions:1.928<ndh  (7)28.60<νdh  (8) where ndh denotes refractive index at d-line (wavelengthλ=587.6 nm) of the lens, and νdh denotes Abbe number at d-line(wavelength λ=587.6 nm) of the lens.